Advanced Essential Blood Test

Total protein measures all the protein floating in your blood—mainly albumin (made by your liver) and globulins (including antibodies from your immune system). This gives a general overview of your nutritional status and can hint at liver, kidney, or immune system issues. Low total protein might suggest malnutrition, liver disease affecting protein production, or conditions where you're losing protein. High total protein can occur with chronic inflammation, infections, or certain blood disorders. It's a useful general health marker that complements the more specific tests. Results outside the normal range may need a follow-up with your GP.

TSH is made by your pituitary gland and tells your thyroid how much hormone to produce. It works like a thermostat—when thyroid hormones are low, TSH goes up to stimulate more production; when they're high, TSH drops. This makes TSH the most sensitive marker for thyroid problems. A high TSH typically suggests an underactive thyroid (hypothyroidism)—your pituitary is shouting at a sluggish thyroid to work harder. A low TSH suggests an overactive thyroid (hyperthyroidism)—the pituitary backs off because there's already too much hormone. It's usually the first thyroid test to become abnormal. Results outside the normal range may need a follow-up with your GP.

Free T4 is the unbound, active form of thyroxine—the main hormone your thyroid produces. Most T4 in your blood is bound to proteins and inactive; free T4 is what's actually available to your cells. T4 is like a storage hormone—it gets converted to the more active T3 in your tissues. Low free T4 with high TSH confirms hypothyroidism. High free T4 with low TSH confirms hyperthyroidism. Sometimes T4 is normal but TSH is off, suggesting your thyroid is working hard to compensate for early dysfunction. Checking both gives a clearer picture than either alone. Results outside the normal range may need a follow-up with your GP.

Free T3 is the active thyroid hormone that actually does the work in your cells—controlling metabolism, energy production, heart rate, and body temperature. Most T3 is made by converting T4 in your tissues rather than directly by the thyroid. Some people have normal T4 but struggle to convert it to T3, which can cause hypothyroid symptoms despite 'normal' thyroid tests. Checking T3 alongside TSH and T4 gives the most complete thyroid picture. T3 is particularly useful for detecting hyperthyroidism, where it often rises before T4 does. Results outside the normal range may need a follow-up with your GP.

Serum iron measures the amount of iron circulating in your blood right now. Your body needs iron to make haemoglobin—the protein in red blood cells that carries oxygen—and it's also essential for energy production, immune function, and brain health. Serum iron fluctuates throughout the day and can be affected by recent meals, so it's best interpreted alongside ferritin and transferrin saturation rather than on its own. Low iron is common, especially in women, vegetarians, and people with heavy periods or absorption issues. Very high iron can indicate iron overload conditions. Results outside the normal range may need a follow-up with your GP.

TIBC measures how much transferrin—the protein that carries iron around your blood—is available to bind iron. Think of it as measuring the 'empty seats' on the iron transport system. When iron stores are low, your body makes more transferrin to capture every bit of iron it can, so TIBC goes up. When iron stores are high, there's less need for transport capacity, so TIBC goes down. High TIBC with low iron strongly suggests iron deficiency. Low TIBC can occur with iron overload, chronic disease, or liver problems. Results outside the normal range may need a follow-up with your GP.

Transferrin saturation tells you what percentage of your iron-carrying capacity is actually being used. It's calculated from your serum iron and TIBC. Low saturation (lots of empty seats) suggests iron deficiency. High saturation (nearly all seats full) can indicate iron overload—too much iron relative to carrying capacity. In haemochromatosis (genetic iron overload), transferrin saturation is often one of the first markers to become abnormal. Normal saturation is typically 20-45%. It's a useful way to spot both deficiency and overload. Results outside the normal range may need a follow-up with your GP.

Ferritin is a protein that stores iron in your cells, and blood ferritin reflects those stores—it's the best single marker of your iron reserves. Think of it as your iron savings account. Low ferritin is often the first sign of depleting iron stores, even before you become anaemic. It's common in women with heavy periods, vegetarians, and endurance athletes. However, ferritin also rises with inflammation, infection, and liver disease—so a 'normal' ferritin doesn't always rule out iron deficiency when these are present. Very high ferritin can indicate iron overload or chronic inflammation. Results outside the normal range may need a follow-up with your GP.

ALT is an enzyme that lives mainly inside your liver cells. When those cells are damaged or inflamed, ALT leaks into your bloodstream—so elevated levels signal that something's irritating your liver. Common culprits include fatty liver disease (increasingly common with modern diets), alcohol, viral hepatitis, and certain medications. ALT is often the first liver marker to rise when there's a problem, making it useful for early detection. A one-off mild elevation might not mean much, but persistently raised ALT usually warrants investigation. Results outside the normal range may need a follow-up with your GP.

AST is another liver enzyme, but unlike ALT, it's also found in your heart, muscles, kidneys, and brain. This means raised AST isn't as specific to the liver—it could come from muscle damage after intense exercise, a heart issue, or other sources. Doctors look at the ratio between AST and ALT to help narrow things down. When AST is significantly higher than ALT, it can point to alcohol-related liver damage. When both are raised but ALT leads, it often suggests fatty liver or viral hepatitis. Results outside the normal range may need a follow-up with your GP.

GGT is an enzyme concentrated in your liver and bile ducts, and it's particularly sensitive to alcohol—even moderate regular drinking can push it up. This makes it useful for spotting alcohol-related liver stress before other markers budge. GGT also rises with bile duct problems, fatty liver, and certain medications. It's often used alongside ALP to determine whether a raised ALP is coming from liver or bones (bone issues don't affect GGT). An isolated raised GGT often prompts a look at alcohol intake or fatty liver. Results outside the normal range may need a follow-up with your GP.

ALP is an enzyme found mainly in your liver and bones, with smaller amounts in kidneys and gut. In the liver, it's concentrated in cells lining the bile ducts. Elevated ALP often points to bile duct issues or bone conditions, rather than liver cell damage specifically. It's naturally higher in children and teenagers (growing bones) and during pregnancy. In adults, a raised ALP alongside other abnormal liver markers usually prompts further investigation. When ALP is raised but GGT is normal, the source is more likely bone than liver. Results outside the normal range may need a follow-up with your GP.

Creatinine is a waste product from the normal wear and tear of your muscles. Your body produces it at a fairly steady rate, and healthy kidneys filter it out into your urine. Because production is consistent and clearance depends on kidney function, creatinine is a reliable marker for how well your kidneys are working. Higher levels suggest your kidneys aren't filtering as efficiently as they should. That said, creatinine is affected by muscle mass—muscular people may naturally run higher. Dehydration and certain medications can also temporarily bump it up. Results outside the normal range may need a follow-up with your GP.

eGFR (estimated Glomerular Filtration Rate) calculates how much blood your kidneys filter per minute—essentially measuring their efficiency. It's worked out from your creatinine level along with your age, sex, and ethnicity. A higher number is better: above 90 is generally normal, while lower numbers suggest declining kidney function. The beauty of eGFR is that it can detect kidney problems earlier than creatinine alone, often before you'd notice any symptoms. It's especially important to monitor if you have diabetes, high blood pressure, or take medications that can affect kidneys. Results outside the normal range may need a follow-up with your GP.

Total cholesterol is the sum of all cholesterol in your blood—HDL ('good'), LDL ('bad'), and other types combined. Your body needs cholesterol to build cell membranes, make hormones like oestrogen and testosterone, and produce vitamin D. The key is balance rather than just the total number. This gives you a starting point, but looking at the breakdown between HDL and LDL tells you much more about your actual cardiovascular risk. Diet, exercise, genetics, and lifestyle all play a role. Results outside the normal range may need a follow-up with your GP.

LDL (low-density lipoprotein) is the 'bad' cholesterol because it deposits cholesterol into your artery walls, where it can build up into plaques over time. This process—atherosclerosis—narrows your arteries and increases heart attack and stroke risk. The good news is LDL responds well to lifestyle changes: eating more fibre, reducing saturated fat, exercising regularly, and maintaining a healthy weight. Some people also have genetic factors that keep LDL stubbornly high. Lower is generally better for this marker. Results outside the normal range may need a follow-up with your GP.

HDL (high-density lipoprotein) is the 'good' cholesterol—you want this one higher. It acts like a cleanup crew, scooping up excess cholesterol from your arteries and ferrying it back to your liver for disposal. Higher HDL levels are linked to lower cardiovascular risk. Exercise is one of the best ways to raise HDL, along with eating healthy fats like olive oil, avocados, and nuts. Smoking tanks your HDL, so quitting is one of the fastest ways to improve this number. Results outside the normal range may need a follow-up with your GP.

Non-HDL cholesterol is your total cholesterol minus your HDL—capturing all the potentially harmful types in one convenient number. Many doctors now prefer this to LDL alone because it includes other problematic particles like VLDL that also contribute to artery damage. It stays accurate even if you haven't fasted perfectly. The target for most people is below 4 mmol/L, though your ideal may vary depending on other risk factors. Think of it as the 'everything except the good stuff' measurement. Results outside the normal range may need a follow-up with your GP.

This ratio divides your total cholesterol by your HDL, giving you a quick cardiovascular risk snapshot. A lower ratio is better—it means more of your cholesterol is the helpful kind. Someone with moderately high total cholesterol but excellent HDL might actually have a healthier ratio than someone with lower total cholesterol but poor HDL. Most guidelines suggest aiming for a ratio below 4, with below 3.5 being ideal. It's a useful number for tracking progress over time. Results outside the normal range may need a follow-up with your GP.

Triglycerides are the most common type of fat in your blood. When you eat more calories than you need, your body converts the excess into triglycerides and stores them in fat cells. They're heavily influenced by recent food—especially sugar, refined carbs, and alcohol—which is why fasting matters for this test. Consistently high triglycerides increase cardiovascular risk and can contribute to fatty liver. Cutting back on sugar and alcohol usually brings them down quite effectively. Results outside the normal range may need a follow-up with your GP.

HbA1c (glycated haemoglobin) measures your average blood sugar over the past 2-3 months by looking at how much glucose has attached to haemoglobin in your red blood cells. Unlike a finger-prick glucose test that shows what's happening right now, HbA1c gives you the bigger picture—it won't be thrown off by what you ate yesterday. It's the gold standard for diabetes screening: below 42 mmol/mol is normal, 42-47 indicates prediabetes, and 48 or above is in the diabetic range. Even without diabetes, it helps you understand how your diet affects blood sugar. Results outside the normal range may need a follow-up with your GP.

Vitamin D is crucial for calcium absorption and bone health, but it also supports immune function, muscle strength, and mood regulation. Your skin makes it when exposed to sunlight, which is why deficiency is incredibly common in the UK, especially from October to March. Symptoms of low vitamin D include tiredness, muscle weakness, bone pain, and low mood—often vague enough to be blamed on other things. Food sources like oily fish, eggs, and fortified foods help, but many people need supplements. This test measures 25-OH vitamin D, the main circulating form. Results outside the normal range may need a follow-up with your GP.

Active B12 (holotranscobalamin) measures the form of B12 your body can actually use—it's more accurate than total B12 because it shows what's available to your cells. B12 is essential for making red blood cells, keeping your nervous system healthy, and producing DNA. Deficiency can sneak up slowly, causing fatigue, weakness, pins and needles, memory problems, and mood changes. Vegans and vegetarians are at higher risk since B12 comes mainly from animal foods. Absorption also decreases with age and certain gut conditions. Results outside the normal range may need a follow-up with your GP.

Folate (vitamin B9) is essential for DNA synthesis, cell division, and red blood cell formation—making it particularly important during pregnancy for preventing neural tube defects. It works closely with vitamin B12; the two need each other to function properly. Deficiency can cause anaemia with symptoms like tiredness and weakness. Good dietary sources include leafy greens, legumes, and fortified cereals. Unlike B12, your body doesn't store much folate, so you need regular intake. Low folate can be caused by poor diet, excessive alcohol, certain medications, or malabsorption. Results outside the normal range may need a follow-up with your GP.

Vitamin B1 (thiamine) is essential for energy metabolism—helping your cells convert carbohydrates into usable energy. It's also crucial for nerve function and muscle contraction, including your heart muscle. Deficiency is rare in people eating a varied diet but can occur with excessive alcohol use, very restrictive diets, and malabsorption conditions. Severe deficiency causes beriberi (affecting the heart and nervous system) or Wernicke-Korsakoff syndrome (a serious brain condition). Good sources include whole grains, pork, legumes, and fortified cereals. Results outside the normal range may need a follow-up with your GP.

Magnesium is involved in over 300 enzyme reactions in your body—essential for muscle and nerve function, blood sugar control, blood pressure regulation, and making protein and bone. Despite being so important, deficiency is surprisingly common because modern diets often fall short and stress depletes it faster. Low magnesium can cause muscle cramps, twitches, fatigue, and poor sleep. The tricky thing is that blood magnesium only shows what's circulating—most is stored in bones and cells, so blood levels can look normal even when stores are low. Results outside the normal range may need a follow-up with your GP.

Zinc is essential for immune function, wound healing, protein synthesis, and DNA production. It also plays a role in taste and smell perception. Your body doesn't store zinc, so you need regular dietary intake. Deficiency can cause poor wound healing, weakened immunity, hair loss, skin problems, and altered taste. Vegetarians and vegans may be at higher risk since zinc from plant foods is less well absorbed. Excessive zinc supplementation can interfere with copper absorption and cause problems too, so balance matters. Results outside the normal range may need a follow-up with your GP.

Copper is a trace mineral essential for iron metabolism (helping you absorb and use iron properly), connective tissue formation, energy production, and nervous system function. Deficiency is uncommon but can cause anaemia that doesn't respond to iron supplements, nerve problems, and weakened immunity. It can occur with excessive zinc supplementation (zinc and copper compete for absorption), malabsorption conditions, and very restrictive diets. Good sources include shellfish, nuts, seeds, organ meats, and chocolate. Checking copper alongside iron can help explain unexplained anaemia. 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 every tissue in your body. It's what makes blood red. Low haemoglobin—anaemia—can leave you feeling exhausted, breathless, dizzy, and looking pale because your tissues aren't getting enough oxygen. Causes range from iron deficiency (the most common) to B12 or folate deficiency, chronic disease, or blood loss. High haemoglobin can occur with dehydration, living at altitude, or conditions where your body makes too many red blood cells. Results outside the normal range may need a follow-up with your GP.

This counts the actual number of red blood cells in a volume of your blood. Red cells are made in your bone marrow and live for about 120 days before being recycled. Low red cell count can indicate anaemia from various causes—blood loss, nutritional deficiencies, bone marrow problems, or chronic disease. High red cell count can occur with dehydration, living at altitude, lung disease (where your body compensates for low oxygen), or bone marrow conditions that overproduce cells. It's interpreted alongside haemoglobin and the red cell indices. Results outside the normal range may need a follow-up with your GP.

Haematocrit measures what percentage of your blood volume is made up of red blood cells. If your haematocrit is 45%, that means 45% of your blood is red cells and the rest is plasma plus other cells. It tends to track with haemoglobin—low haematocrit usually means anaemia, high haematocrit can mean dehydration or overproduction of red cells. Athletes sometimes have higher haematocrit from training adaptations. It's a useful companion to haemoglobin that helps confirm anaemia and assess hydration status. Results outside the normal range may need a follow-up with your GP.

MCV measures the average size of your red blood cells and is one of the most useful markers for working out what type of anaemia someone has. Small cells (low MCV, 'microcytic') typically point to iron deficiency or thalassaemia. Large cells (high MCV, 'macrocytic') suggest B12 or folate deficiency, or sometimes excess alcohol. Normal-sized cells with low haemoglobin ('normocytic' anaemia) can occur with chronic disease, kidney problems, or recent blood loss. MCV helps narrow down the possibilities. Results outside the normal range may need a follow-up with your GP.

MCH tells you the average amount of haemoglobin inside each red blood cell—how 'full' of haemoglobin your red cells are. Low MCH means your cells are carrying less oxygen-carrying capacity—typically seen with iron deficiency anaemia, where cells are small and pale. High MCH suggests larger-than-normal cells packed with haemoglobin, which happens with B12 or folate deficiency. MCH works together with MCV and MCHC to help pinpoint the cause of anaemia. Results outside the normal range may need a follow-up with your GP.

MCHC measures the concentration of haemoglobin within your red blood cells—how densely packed with haemoglobin they are. While MCH looks at the total amount per cell, MCHC accounts for cell size too. Low MCHC produces 'hypochromic' (pale) cells, typically seen in iron deficiency where cells can't make enough haemoglobin. High MCHC is less common but can occur in conditions where red cells are abnormally shaped. It's a useful confirmatory marker alongside MCH and MCV. Results outside the normal range may need a follow-up with your GP.

RDW measures how much variation there is in the size of your red blood cells. Normally, red cells are fairly uniform in size, so a low RDW is good. A high RDW means you have a mix of different-sized cells—some big, some small—which can happen when your bone marrow is producing abnormal cells or when you have mixed causes of anaemia (like combined iron and B12 deficiency). It's useful for distinguishing between different types of anaemia and can be an early marker of nutritional deficiencies. Results outside the normal range may need a follow-up with your GP.

White blood cells are your immune system's soldiers, defending you against infections, viruses, and other invaders. A raised count often signals your immune system is fighting something—an infection, inflammation, or even stress. Very high counts can occasionally indicate blood disorders. A low count might suggest viral infections, bone marrow problems, or immune deficiencies—it can leave you more vulnerable to infections. Some medications and autoimmune conditions also affect white cell numbers. Results outside the normal range may need a follow-up with your GP.

Neutrophils are the most abundant type of white blood cell and your first responders to bacterial infections. They're like the infantry of your immune system—quick to arrive at sites of infection or injury, where they engulf and destroy bacteria. High neutrophils often indicate bacterial infection or inflammation. Low neutrophils (neutropenia) can occur with viral infections, certain medications (especially chemotherapy), or bone marrow problems—it increases your risk of bacterial infections. Results outside the normal range may need a follow-up with your GP.

Lymphocytes are white blood cells that handle the more sophisticated parts of immunity—they include T-cells (which kill infected cells and coordinate immune responses), B-cells (which make antibodies), and natural killer cells. High lymphocytes often occur with viral infections (your body's fighting the virus), some autoimmune conditions, or occasionally lymphoma. Low lymphocytes can occur with HIV, after chemotherapy, or with severe infections. The balance between neutrophils and lymphocytes can help distinguish viral from bacterial infections. Results outside the normal range may need a follow-up with your GP.

Monocytes are white blood cells that travel through your bloodstream and then move into tissues where they become macrophages—large cells that engulf and digest bacteria, dead cells, and debris. They're like the cleanup crew after an infection. High monocytes can occur with chronic infections (like tuberculosis), autoimmune conditions, and some blood cancers. Mildly elevated monocytes during recovery from an infection is normal—they're cleaning up. Results outside the normal range may need a follow-up with your GP.

Eosinophils are white blood cells particularly involved in fighting parasites and in allergic reactions. High eosinophils (eosinophilia) commonly occur with allergies, asthma, eczema, hay fever, and parasitic infections. They can also be elevated with certain autoimmune conditions and some blood disorders. If you have seasonal allergies, don't be surprised to see elevated eosinophils during pollen season. Very high levels warrant investigation. Results outside the normal range may need a follow-up with your GP.

Platelets are tiny cell fragments that clump together to form clots and stop bleeding. Too few platelets (thrombocytopenia) can mean bruising easily and bleeding that's hard to stop—causes include viral infections, certain medications, autoimmune conditions, or bone marrow problems. Too many platelets (thrombocytosis) can increase clotting risk—sometimes it's reactive (responding to inflammation or iron deficiency) and sometimes indicates a bone marrow condition. Platelet count is a basic but important marker of your clotting system. Results outside the normal range may need a follow-up with your GP.

CRP is a protein produced by your liver in response to inflammation anywhere in your body. It rises quickly with infections, injuries, and inflammatory conditions, making it a useful general marker that something's going on—though it doesn't tell you where or what. High CRP can occur with infections, autoimmune diseases, inflammatory bowel disease, and tissue injury. It's also useful for monitoring whether treatments for inflammatory conditions are working. CRP typically returns to normal once the inflammation resolves. Results outside the normal range may need a follow-up with your GP.

High-sensitivity CRP is the same protein as regular CRP, but measured with a more sensitive test that can detect lower levels. This makes it useful for assessing low-grade chronic inflammation—the kind linked to cardiovascular disease risk. While regular CRP picks up obvious infections and inflammation, hs-CRP can detect the subtle, ongoing inflammation that contributes to artery damage over time. Studies show that people with higher hs-CRP have increased risk of heart attacks and strokes, even when cholesterol is normal. It adds another dimension to cardiovascular risk assessment. Results outside the normal range may need a follow-up with your GP.