Whether you are investigating a specific health concern, optimising your sports performance, or simply seeking peace of mind about your general wellbeing, a blood test is one of the most effective tools available. To help you feel confident and prepared, we have put together this comprehensive guide explaining exactly how a blood test works.
How Blood is Collected
There are two primary methods for collecting a blood sample. The right method for you depends on the test you are taking and the volume of blood required.
The two main blood collection methods: venous sample (left) and finger-prick sample (right)
💉 Venous Blood Sample
A qualified healthcare professional draws blood from a vein, typically in the crook of your arm. This allows for a larger volume of blood to be collected, which is necessary when testing a wide range of biomarkers simultaneously. The blood is collected into one or more colour-coded vials.
☝ Finger-Prick Sample
A less invasive option you can do yourself at home. It involves using a small lancet to prick the tip of your finger and collecting a few drops of blood into a micro-vial. Convenient and quick, though not all biomarkers can be tested this way, particularly those requiring larger volumes.
Where Can I Get a Blood Test?
You have several options when it comes to getting a blood test in the UK.
NHS Blood Tests
The NHS provides blood testing services at GP surgeries and local hospitals, primarily to investigate symptoms and diagnose medical conditions. These are typically venous blood draws performed by a trained clinician. Depending on demand, there may be a waiting period for an appointment.
Private Blood Tests with Medi Test Direct
Private testing offers flexibility and convenience. With Medi Test Direct, you can order tests online and choose how you want to provide your sample. You can opt for a home finger-prick kit delivered to your door, or visit one of our 365+ partner clinics across the UK to have a venous sample taken by a qualified phlebotomist. All our partner laboratories are fully UKAS accredited and adhere to the highest clinical standards.
365+ Partner Clinics Nationwide
All Medi Test Direct partner clinics are staffed by qualified phlebotomists. Enter your postcode on our homepage to find your nearest clinic for a venous blood draw.
Preparing for Your Blood Test
Proper preparation can make your blood test smoother and help ensure the most accurate results. Whether you are doing a finger-prick test at home or visiting a clinic, the following steps will help increase blood flow and make the collection process easier.
Four simple steps to prepare for a successful blood collection
Drinking a large glass of water in the hour before your test helps your veins become more prominent and your blood flow more freely. Having a warm shower or washing your hands in warm water also helps. If you are doing a finger-prick test, gently massage your hand down to your fingertip several times to warm the area. Finally, standing up and keeping your hand pointed downwards lets gravity assist the blood flow.
Best Time to Test: Morning
Unless your specific test instructions state otherwise, take your blood sample in the morning. Hormone levels peak early in the day, and posting your sample the same day ensures it reaches the lab quickly.
Common Questions
Understanding Sample Errors
Occasionally, a blood sample cannot be processed by the laboratory. Understanding the most common causes can help you avoid them and ensure a smooth testing experience.
Clotted Sample
Occurs when blood clots before mixing with the anticoagulant in the tube. Always gently invert the tube several times after collection — never shake it.
Haemolysed Sample
Happens when red blood cells burst, spoiling the sample. Avoid squeezing your finger too hard during a home test and never vigorously shake the tube.
Insufficient Sample
If not enough blood is collected, the lab cannot run all requested tests. Follow the preparation tips above to maximise blood flow before collection.
By following the preparation guidelines and collection instructions carefully, you can minimise the risk of sample errors and ensure your results are accurate and reliable.