Advanced Sports Hormone Blood Test Kit

Total cholesterol measures all cholesterol circulating in your blood—HDL, LDL, and VLDL combined. For athletes and bodybuilders, cholesterol is particularly important because it's the raw material your body uses to manufacture testosterone and other steroid hormones. Your liver produces most cholesterol, with some coming from diet. While very low cholesterol can theoretically limit hormone production, most athletes have adequate levels. The concern is usually the opposite—elevated cholesterol increasing cardiovascular risk. Anabolic steroids commonly disrupt lipid profiles, often lowering protective HDL while raising LDL, which is why monitoring is important. Results outside the normal range may need a follow-up with your GP.

Low-density lipoprotein (LDL) cholesterol transports cholesterol from your liver to tissues throughout your body. While necessary for hormone production and cell membrane maintenance, excess LDL deposits cholesterol in artery walls, forming plaques that narrow vessels and increase heart attack and stroke risk. Anabolic steroids—particularly oral compounds that pass through the liver—commonly raise LDL, sometimes dramatically. This effect can persist for weeks to months after stopping. Combined with the HDL-lowering effect, steroid use can create an unfavourable lipid profile that accelerates cardiovascular disease if unchecked. Monitoring LDL helps you make informed decisions about health management. Results outside the normal range may need a follow-up with your GP.

High-density lipoprotein (HDL) cholesterol is your cardiovascular system's cleanup crew—it collects excess cholesterol from artery walls and tissues and returns it to the liver for recycling or disposal. Higher HDL is protective; levels below 1.0 mmol/L in men or 1.2 mmol/L in women indicate increased cardiovascular risk. HDL is one of the most sensitive markers affected by anabolic steroid use—even modest doses can slash HDL by 50% or more, sometimes to single-digit levels. This is one of the primary mechanisms by which long-term steroid use increases cardiovascular risk. Cardiovascular exercise, omega-3 fatty acids, and time off cycle can help HDL recover. Results outside the normal range may need a follow-up with your GP.

Non-HDL cholesterol is calculated by subtracting HDL from total cholesterol, capturing all the potentially harmful cholesterol particles in one number—LDL, VLDL, IDL, and lipoprotein(a). Many cardiologists consider non-HDL a better predictor of cardiovascular risk than LDL alone, especially when triglycerides are elevated (which affects LDL calculation accuracy). For athletes using performance-enhancing substances, non-HDL provides a comprehensive view of atherogenic cholesterol that isn't confounded by triglyceride fluctuations from diet or training. A non-HDL below 3.8 mmol/L is generally desirable; above 4.9 mmol/L indicates significantly increased cardiovascular risk. Results outside the normal range may need a follow-up with your GP.

The total cholesterol to HDL ratio expresses what proportion of your total cholesterol is the protective HDL type versus potentially harmful types. It's calculated by dividing total cholesterol by HDL. A ratio below 4 is considered good; above 6 indicates significantly elevated cardiovascular risk. This ratio often becomes concerning in steroid users because HDL drops substantially while total cholesterol may stay the same or rise—pushing the ratio upward even when the absolute numbers don't look alarming. Tracking this ratio over time helps you understand your cardiovascular risk trajectory. Results outside the normal range may need a follow-up with your GP.

Triglycerides are fats that circulate in your blood, providing energy to muscles between meals. They come from dietary fat and from your liver converting excess carbohydrates and calories. For athletes, moderately elevated triglycerides during a bulking phase with high calorie intake aren't unusual. However, persistently high triglycerides (above 2.3 mmol/L) increase cardiovascular risk and may indicate insulin resistance or metabolic issues. Some anabolic compounds affect triglyceride metabolism, and growth hormone use can also elevate them. Very high triglycerides (above 10 mmol/L) create acute risk of pancreatitis. Triglycerides respond well to dietary changes—reducing refined carbohydrates, alcohol, and excess calories typically brings them down. Results outside the normal range may need a follow-up with your GP.

Platelets are cell fragments produced by your bone marrow that form clots to stop bleeding when you're injured. The normal range is 150-400 × 10⁹/L. Low platelets (thrombocytopenia) increase bleeding risk, while very high platelets (thrombocytosis) can increase clotting risk. Some performance-enhancing substances can affect platelet production—certain anabolic steroids may increase platelet counts, while others can suppress them. Platelet count is also part of the overall picture when assessing blood viscosity and clotting risk alongside haematocrit and haemoglobin. Results outside the normal range may need a follow-up with your GP.

Mean platelet volume measures the average size of your platelets. Larger platelets are generally younger, more reactive, and more effective at clotting. MPV provides information about platelet production in your bone marrow. A high MPV with low platelet count suggests platelets are being destroyed or consumed faster than they're made, triggering the bone marrow to release larger, younger platelets. A low MPV might indicate bone marrow suppression affecting platelet production. MPV adds context to the platelet count and helps interpret overall clotting status. Results outside the normal range may need a follow-up with your GP.

HbA1c measures the percentage of haemoglobin with glucose attached, reflecting your average blood sugar over the past 2-3 months. It's unaffected by what you ate yesterday or whether you fasted. For athletes, good blood sugar control supports recovery, reduces inflammation, and optimises body composition. HbA1c below 42 mmol/mol is normal; 42-47 indicates prediabetes; 48+ is diagnostic of diabetes. Growth hormone use can impair insulin sensitivity and raise HbA1c. Insulin use (by those trying to enhance anabolism) obviously affects glucose control and carries serious risks if not managed carefully. Even without these substances, high-calorie bulking diets can push blood sugar higher over time. Monitoring HbA1c helps you catch developing insulin resistance early. Results outside the normal range may need a follow-up with your GP.

Testosterone is the primary anabolic hormone driving muscle protein synthesis, strength adaptation, recovery, training motivation, and libido. Total testosterone measures all testosterone in your blood—free, albumin-bound, and SHBG-bound. In men, the normal range is typically 8.6-29 nmol/L, though optimal for performance is debated. Low testosterone causes fatigue, poor recovery, muscle loss, low mood, and reduced training drive. If you're using exogenous testosterone or anabolic steroids, total testosterone will be elevated (sometimes dramatically) while you're on cycle—that's expected. The more important question is what happens to your natural production when you stop. If you're natural and experiencing low testosterone symptoms, this test helps identify whether hormones are contributing. Results outside the normal range may need a follow-up with your GP.

Free testosterone is the portion not bound to proteins—only about 2-3% of total testosterone, but it's the biologically active form that can enter cells and bind to androgen receptors. This test calculates free testosterone from total testosterone and SHBG using a validated algorithm. Free testosterone matters because you can have normal total testosterone but low free testosterone if SHBG is high (binding up the available hormone), or adequate free testosterone despite borderline-low total if SHBG is low. For assessing anabolic potential and correlating with symptoms, free testosterone often tells a more useful story than total testosterone alone. Results outside the normal range may need a follow-up with your GP.

SHBG is a protein made by your liver that binds testosterone and oestradiol, making them inactive. High SHBG reduces the amount of free testosterone available to your tissues—you might have 'normal' total testosterone but still experience low-T symptoms because most of it is bound up. SHBG increases with age, hyperthyroidism, liver disease, and certain medications. It decreases with obesity, insulin resistance, hypothyroidism, and—notably—anabolic steroid use. Low SHBG from steroid use means more free testosterone but also faster clearance. SHBG is also needed to calculate free testosterone and the free androgen index. Results outside the normal range may need a follow-up with your GP.

The free androgen index is calculated as (total testosterone ÷ SHBG) × 100, providing a ratio that estimates androgen activity in your body. A higher FAI indicates more biologically available testosterone relative to binding proteins. FAI is particularly useful in women for assessing hyperandrogenism (e.g., in PCOS), but in men it helps contextualise testosterone status relative to SHBG. If you're using anabolic steroids, FAI will typically be very high because testosterone is elevated while SHBG is suppressed—both pushing the ratio upward. In natural athletes, FAI helps distinguish between those with genuinely low androgens versus those with high SHBG limiting their free testosterone. Results outside the normal range may need a follow-up with your GP.

LH is produced by your pituitary gland and signals your testicles (Leydig cells) to produce testosterone. It's the key controller of natural testosterone production. LH tells you whether your pituitary is sending the signal or not. High LH with low testosterone indicates primary hypogonadism—your pituitary is shouting but your testicles aren't responding. Low LH with low testosterone indicates secondary hypogonadism—the signal isn't being sent. If you're using exogenous testosterone or anabolic steroids, your LH will be suppressed to very low or undetectable levels—this is expected because your pituitary senses the external hormones and stops calling for more. LH recovery after stopping steroids is a key marker of HPTA (hypothalamic-pituitary-testicular axis) recovery. Results outside the normal range may need a follow-up with your GP.

FSH is produced by your pituitary gland and stimulates the Sertoli cells in your testicles, which support sperm production (spermatogenesis). While LH drives testosterone production, FSH drives fertility. Like LH, FSH is suppressed by exogenous testosterone and anabolic steroids—often to undetectable levels. This suppression impairs sperm production, which is why steroid use commonly causes temporary infertility. FSH recovery after stopping is typically slower than LH recovery. In natural athletes, low FSH combined with low testosterone suggests a pituitary problem. High FSH with low testosterone suggests primary testicular failure. FSH provides important context alongside LH for understanding your hormonal axis. Results outside the normal range may need a follow-up with your GP.

Oestradiol is the primary oestrogen, and yes, men produce it too—it's made by converting testosterone through the aromatase enzyme, mainly in fat tissue. Some oestradiol is necessary for bone health, joint function, libido, and cardiovascular protection. However, too much causes water retention, bloating, mood changes, and gynaecomastia (breast tissue growth). When using aromatisable steroids (testosterone, dianabol, deca, etc.), oestradiol often rises proportionally—sometimes to problematic levels. This is why some users employ aromatase inhibitors, though crashing oestradiol too low creates its own problems (joint pain, low libido, cardiovascular risk). Monitoring oestradiol helps you find the balance. Results outside the normal range may need a follow-up with your GP.

Cortisol is your body's primary stress hormone, produced by your adrenal glands in response to physical and psychological stress. It has important functions—mobilising energy, regulating inflammation, supporting alertness—but chronically elevated cortisol is catabolic, breaking down muscle tissue, impairing recovery, suppressing immune function, promoting fat storage (especially abdominal), and disrupting sleep. Overtraining syndrome typically features elevated cortisol. Conversely, very low cortisol can indicate adrenal fatigue or suppression from corticosteroid medications. Cortisol follows a circadian rhythm—highest in the morning, lowest at night—which is why morning testing gives the most meaningful baseline. A healthy testosterone-to-cortisol ratio favours anabolism over catabolism. Results outside the normal range may need a follow-up with your GP.

High-sensitivity CRP measures low-level inflammation throughout your body. CRP is produced by your liver in response to inflammatory signals. The 'high-sensitivity' assay detects the subtle elevations relevant to cardiovascular risk and chronic low-grade inflammation, rather than just the dramatic elevations seen with acute infection or injury. For athletes, persistently elevated hs-CRP may indicate inadequate recovery, overtraining, chronic injury, or systemic inflammation from other causes. hs-CRP also serves as a cardiovascular risk marker—chronic inflammation contributes to atherosclerosis. Some performance-enhancing substances can affect inflammatory markers in both directions. An hs-CRP below 1 mg/L is low cardiovascular risk; 1-3 is moderate; above 3 is higher risk (or may indicate acute inflammation). Results outside the normal range may need a follow-up with your GP.

Serum iron measures the amount of iron circulating in your blood, bound to the transport protein transferrin. Iron is essential for making haemoglobin, which carries oxygen to your working muscles. Low iron causes fatigue, reduced endurance, impaired recovery, and eventually anaemia. Athletes have increased iron requirements due to losses through sweat, GI bleeding from intense exercise, and 'foot-strike haemolysis' in runners. Serum iron fluctuates throughout the day and is affected by recent meals, so it's best interpreted alongside ferritin, TIBC, and transferrin saturation for the complete picture. Results outside the normal range may need a follow-up with your GP.

TIBC measures how much iron your blood could carry if all the transferrin protein was fully loaded. It indirectly reflects transferrin levels. When iron stores are low, your body produces more transferrin to maximise iron capture from your diet—so TIBC rises. When iron stores are adequate or high, less transferrin is needed and TIBC is normal or low. High TIBC typically indicates iron deficiency; your body is ramping up transport capacity to compensate for low stores. Low TIBC can occur with iron overload, chronic disease, or malnutrition. TIBC helps distinguish between different causes of abnormal iron or ferritin levels. Results outside the normal range may need a follow-up with your GP.

Transferrin saturation indicates what percentage of your iron-carrying capacity is actually being used—calculated as (serum iron ÷ TIBC) × 100. Normal saturation is typically 20-50%. Low transferrin saturation (below 20%) indicates iron deficiency—there isn't enough iron to fill the available transport. Very high saturation (above 45-50%) can indicate iron overload, which may be relevant for those supplementing iron aggressively or with hereditary haemochromatosis. For athletes, low transferrin saturation is a more sensitive early marker of iron deficiency than haemoglobin, helping you catch and address the problem before full anaemia develops. Results outside the normal range may need a follow-up with your GP.

Ferritin is the storage form of iron, and blood ferritin reflects your body's iron reserves. It's the most useful single marker for iron status. Low ferritin indicates depleted iron stores and predicts iron deficiency anaemia if not addressed—even before haemoglobin drops. For optimal athletic performance, ferritin above 50 µg/L is often recommended, though the reference range starts much lower. However, ferritin is also an acute phase reactant—it rises with inflammation, infection, and liver disease, which can mask underlying iron deficiency. This is why hs-CRP is included in this panel—if CRP is elevated, ferritin may be falsely reassuring. Very high ferritin (above 300-500) warrants investigation for iron overload or other causes. Results outside the normal range may need a follow-up with your GP.

Urea is a waste product created when your liver breaks down protein. It's filtered by your kidneys and excreted in urine. Elevated urea can indicate increased protein breakdown (from high protein intake, muscle damage, or catabolic states), dehydration (concentrated blood), or reduced kidney function. Athletes on high-protein diets commonly have urea at the higher end of normal—this is usually fine if kidney function (eGFR) is normal. However, significantly elevated urea alongside rising creatinine and falling eGFR suggests the kidneys are struggling. Some oral anabolic steroids and other substances can stress the kidneys, making urea monitoring worthwhile. Results outside the normal range may need a follow-up with your GP.

Creatinine is a waste product from the normal breakdown of creatine in muscle tissue. It's produced at a fairly constant rate based on your muscle mass and filtered by your kidneys. Because muscular athletes have more muscle mass generating creatinine, they naturally run higher creatinine levels than sedentary people—this doesn't necessarily indicate kidney problems. However, the formula used to estimate kidney function (eGFR) doesn't account for high muscle mass, so it may underestimate kidney function in muscular individuals. Look at the trend over time rather than single values. A progressive rise in creatinine with declining eGFR is concerning and warrants further investigation. Results outside the normal range may need a follow-up with your GP.

eGFR estimates how efficiently your kidneys filter waste from your blood, calculated from creatinine, age, and sex. An eGFR above 90 mL/min indicates normal kidney function; 60-89 is mildly reduced; below 60 suggests more significant kidney disease. However, eGFR has limitations for athletes—because it's calculated from creatinine, and muscular individuals produce more creatinine, eGFR can be falsely low in people with high muscle mass. A muscular bodybuilder might show eGFR of 70-80 when their actual kidney function is completely normal. Track your trend over time; if eGFR is stable at your personal baseline, that's more reassuring than the absolute number. Results outside the normal range may need a follow-up with your GP.

Sodium is the primary electrolyte maintaining fluid balance outside your cells. It regulates blood pressure, nerve impulse transmission, and muscle contraction. The normal range is tightly controlled at 136-145 mmol/L. Low sodium (hyponatraemia) can occur with excessive water intake, diuretic use, or certain hormonal conditions—it causes confusion, muscle cramps, and in severe cases, dangerous brain swelling. High sodium (hypernatraemia) typically indicates dehydration. Some athletes manipulate sodium and water for competition (weight cuts, 'drying out'), which can be dangerous if taken to extremes. Kidney function, aldosterone, and various substances can all affect sodium regulation. Results outside the normal range may need a follow-up with your GP.

Bilirubin is a yellow pigment produced when your liver processes old red blood cells. It's what makes bruises yellow and causes jaundice when elevated. Mildly elevated bilirubin is often due to Gilbert's syndrome—a common, harmless genetic variation affecting about 5% of people that causes bilirubin to fluctuate, especially with fasting or stress. More significant elevations can indicate liver stress, bile duct obstruction, or excessive red blood cell breakdown. Oral anabolic steroids are hepatotoxic and can elevate bilirubin as part of cholestatic liver injury. If bilirubin rises alongside ALT and GGT while using orals, that's a signal to take liver health seriously. Results outside the normal range may need a follow-up with your GP.

Alkaline phosphatase is an enzyme found in liver, bone, kidney, and intestines. Elevated ALP can come from liver problems (especially bile duct issues) or from increased bone turnover. In young, growing individuals and those doing heavy resistance training, mildly elevated ALP from bone remodelling is common and usually benign. However, ALP elevated alongside ALT and GGT points more toward liver origin. Isolated high ALP with normal liver enzymes suggests bone as the source. Some oral steroids can elevate ALP as part of their hepatotoxic effect. If ALP is very high, your GP might order a GGT to help determine whether it's liver or bone origin. Results outside the normal range may need a follow-up with your GP.

ALT is a liver enzyme that leaks into your blood when liver cells are damaged. It's more specific to the liver than AST. Elevated ALT is one of the earliest signs of liver stress. Oral anabolic steroids—particularly 17-alpha-alkylated compounds like dianabol, anadrol, winstrol, and anavar—are hepatotoxic and commonly elevate ALT, sometimes dramatically. Even injectable steroids can affect liver enzymes, though usually less severely. ALT can also rise from heavy alcohol use, fatty liver disease, certain supplements, and intense exercise (muscle damage releases some ALT). Modest elevations (1-2× normal) may be tolerable short-term, but sustained or marked elevations warrant stopping hepatotoxic compounds. Regular monitoring helps you catch problems early. Results outside the normal range may need a follow-up with your GP.

GGT is a liver enzyme particularly sensitive to bile duct problems and alcohol consumption. It's often elevated before other liver enzymes in early liver stress. GGT also helps distinguish whether elevated ALP is coming from liver or bone—if GGT is also high, liver is more likely the source. Oral steroids commonly elevate GGT as part of their cholestatic effect on bile flow. Heavy alcohol use raises GGT even without other liver enzyme changes. Certain medications and supplements also affect GGT. In the context of performance-enhancing substance use, GGT alongside ALT gives a more complete picture of hepatic stress than either alone. Persistent elevations warrant reducing hepatotoxic exposures. Results outside the normal range may need a follow-up with your GP.

Total protein measures all protein in your blood serum—primarily albumin and globulins combined. It reflects your nutritional status, liver function (which makes albumin), and immune function (which produces immunoglobulins). Low total protein can indicate inadequate protein intake, malabsorption, liver disease, or kidney disease (losing protein in urine). High total protein may indicate dehydration (concentrated blood), chronic inflammation, or certain blood disorders. For athletes on high-protein diets, total protein is usually normal or at the higher end of the range. Significant deviations warrant investigation into the cause. Results outside the normal range may need a follow-up with your GP.

Albumin is the most abundant protein in your blood, produced by your liver. It maintains oncotic pressure (keeping fluid in your blood vessels rather than leaking into tissues), transports hormones and drugs, and serves as a nutritional reserve. Albumin reflects both liver synthetic function and nutritional status. Low albumin causes oedema (fluid retention in tissues) and can indicate liver disease, kidney disease (losing albumin in urine), malnutrition, or chronic inflammation. For athletes, albumin is also used in calculating free testosterone—the algorithm needs albumin levels to estimate how much testosterone is loosely bound versus truly free. Results outside the normal range may need a follow-up with your GP.

Globulins are a diverse group of proteins including immunoglobulins (antibodies), transport proteins, and clotting factors. Globulin is calculated by subtracting albumin from total protein. Elevated globulins often indicate chronic inflammation, infection, or immune system activation—your body is producing more antibodies and inflammatory proteins. In athletes, persistently elevated globulins might suggest overtraining, inadequate recovery, or low-grade chronic inflammation. Low globulins can occur with immune deficiency or certain conditions affecting protein production. The albumin-to-globulin ratio provides additional context about the balance between these protein fractions. Results outside the normal range may need a follow-up with your GP.

Haemoglobin is the protein inside red blood cells that carries oxygen from your lungs to your tissues. It's measured in grams per litre (g/L) or grams per decilitre (g/dL). Low haemoglobin (anaemia) causes fatigue, reduced endurance, and impaired performance—your muscles aren't getting enough oxygen. However, excessively high haemoglobin is also problematic. Testosterone and other androgens stimulate erythropoiesis (red blood cell production), so steroid users commonly develop elevated haemoglobin and haematocrit. This increases blood viscosity—thicker blood that's harder to pump and more prone to clotting. Haemoglobin above 180-185 g/L significantly increases stroke and heart attack risk. If haemoglobin climbs too high, blood donation or therapeutic phlebotomy may be needed. Results outside the normal range may need a follow-up with your GP.

Haematocrit measures what percentage of your blood volume is occupied by red blood cells—the rest is plasma. Normal haematocrit is roughly 40-50% in men, 36-44% in women. Like haemoglobin, haematocrit rises with testosterone and anabolic steroid use as your body produces more red blood cells. Haematocrit above 50-52% indicates polycythaemia—your blood is getting thick. Above 54% is considered dangerous, significantly increasing risk of blood clots, stroke, and heart attack. This is one of the most important safety markers to monitor when using androgens. If haematocrit climbs too high, strategies include reducing dose, taking time off, staying well hydrated, and blood donation. Some steroid users monitor haematocrit more frequently than any other marker for this reason. Results outside the normal range may need a follow-up with your GP.

Red blood cell count measures the actual number of red blood cells per litre of blood. Combined with haemoglobin and haematocrit, it helps characterise your red cell status. Low counts cause anaemia; high counts contribute to blood viscosity. Like haemoglobin and haematocrit, red cell count typically increases with testosterone and anabolic steroid use due to stimulated erythropoiesis. The three measures (haemoglobin, haematocrit, red cell count) usually move together and tell a similar story, though the ratios between them (MCV, MCH, MCHC) can reveal the characteristics of your red cells. Results outside the normal range may need a follow-up with your GP.

MCV measures the average size of your red blood cells, expressed in femtolitres (fL). Normal MCV is approximately 80-100 fL. Low MCV (microcytic cells) typically indicates iron deficiency or thalassaemia—small red cells because there isn't enough haemoglobin to fill them. High MCV (macrocytic cells) suggests vitamin B12 or folate deficiency, alcohol excess, or certain medications—the cells are larger than normal. In the context of steroid use increasing red cell production, MCV helps identify whether the new red cells are normal-sized. If you develop anaemia while training hard, MCV helps determine whether it's from iron deficiency (low MCV) versus B12/folate deficiency (high MCV). Results outside the normal range may need a follow-up with your GP.

TSH is produced by your pituitary gland and controls how much thyroid hormone your thyroid produces. It works in a feedback loop—when thyroid hormones are low, TSH rises to stimulate more production; when thyroid hormones are high, TSH drops. TSH is the most sensitive single marker for thyroid function. High TSH indicates hypothyroidism (underactive thyroid)—your pituitary is calling for more hormone that the thyroid can't deliver. Hypothyroidism causes fatigue, weight gain, cold intolerance, and impaired performance. Low TSH indicates hyperthyroidism (overactive thyroid) or suppression from taking thyroid hormones (T3/T4). Some athletes use T3 to increase metabolic rate for fat loss, which suppresses TSH. Results outside the normal range may need a follow-up with your GP.

Free T3 is the active thyroid hormone that directly affects your cells and metabolism. Most T3 is made by converting T4 in your tissues rather than being produced directly by the thyroid. T3 controls metabolic rate, heat production, and energy expenditure. For athletes, adequate T3 is essential for performance, recovery, and body composition. Low T3 can occur with calorie restriction, chronic stress, illness, or hypothyroidism—your body downregulates metabolism to conserve energy. Some athletes use exogenous T3 (cytomel/liothyronine) to boost metabolism for fat loss, which will show as elevated Free T3 on testing. Chronically elevated T3 from exogenous use can cause muscle loss, bone loss, and heart problems. Results outside the normal range may need a follow-up with your GP.

Free T4 is the unbound, active portion of thyroxine—the main hormone your thyroid produces. T4 acts as a reservoir that gets converted to the more active T3 in your tissues as needed. Measuring Free T4 alongside TSH helps clarify thyroid status. High TSH with low Free T4 confirms hypothyroidism; low TSH with high Free T4 indicates hyperthyroidism or thyroid hormone use. If you're using exogenous T3 but not T4, Free T4 may be low while T3 is high (because your thyroid is suppressed). Low Free T4 with normal T3 and TSH can occur with 'sick euthyroid syndrome' during severe calorie restriction or illness. Results outside the normal range may need a follow-up with your GP.

White blood cells (leukocytes) are your immune system's army, fighting infection and responding to inflammation. The total white cell count measures all types combined. Elevated WBC typically indicates infection, inflammation, or stress response—your body is mobilising immune cells. Very high counts can indicate more serious conditions like leukaemia. Low WBC (leucopenia) increases infection susceptibility and can occur with certain medications, viral infections, or bone marrow problems. Intense exercise temporarily elevates WBC (exercise-induced leukocytosis), which is why resting 48 hours before testing gives a more accurate baseline. Some anabolic compounds can affect white cell production. Results outside the normal range may need a follow-up with your GP.

Neutrophils are the most abundant white blood cells, typically comprising 50-70% of your total white count. They're your first-line defence against bacterial infections, rapidly responding to engulf and destroy pathogens. Elevated neutrophils (neutrophilia) commonly indicate bacterial infection, inflammation, stress response, or corticosteroid use. Low neutrophils (neutropenia) increase infection risk and can occur with certain medications, viral infections, or bone marrow issues. Post-exercise neutrophilia is normal and resolves within hours. In the context of performance enhancement, tracking neutrophils helps monitor immune health alongside other markers. Results outside the normal range may need a follow-up with your GP.