--- title: "Blood tests overview: What to Expect | HealthAnswers" description: "Blood tests check your health, diagnose conditions and monitor medicines; most are quick vein samples that need no preparation, though some require…" url: https://healthanswers.co.uk/tests/blood-tests-overview/ robots: noindex --- # Blood tests overview: What to Expect | HealthAnswers Tests & investigations Blood tests check your health, diagnose conditions and monitor medicines; most are quick vein samples that need no preparation, though some require fasting. Written by HealthAnswers editorial team Medically reviewed by [HealthAnswers UK doctor review panel](https://healthanswers.co.uk/our-doctors/) Reviewed 3 July 2026 ## Quick answer What are blood tests? A blood test is a sample of blood taken from a vein and checked in a laboratory to assess your health, diagnose conditions or monitor medicines. Most blood tests need no special preparation, although some require fasting. A phlebotomist usually takes the sample, and the results are sent to your GP. ## Who is this page for? This page is for people in the UK who want a plain-English overview of Blood tests overview, including when to seek help and what NHS care usually involves. It explains general information, not what is wrong with you personally. ## Who should skip this page? Skip this page if you need a diagnosis, a prescription, or emergency care. It cannot replace a GP, pharmacist, NHS 111 or 999. If you are in immediate danger, call 999; for urgent advice that is not life-threatening, call 111 in England, Scotland or Wales, or use your GP out-of-hours service in Northern Ireland. On this page 4 sections ## Key facts about the blood tests - Routine blood tests check your blood count, kidneys, liver, thyroid and more. - Fasting may be needed for glucose and lipid tests, so follow instructions. - Most blood tests involve a quick sample taken from a vein. - Results usually reach your GP within a few days. - Abnormal results often need a repeat or further tests to confirm. ## What are blood tests for? Blood tests are used to screen for, diagnose and monitor a wide range of conditions. They are among the most common investigations carried out on the NHS. ## What happens when you have blood taken A tourniquet is placed around your arm, the skin is cleaned, and a needle is inserted into a vein to draw the sample. Several tubes may be filled if a number of different tests are needed. ## How to prepare for a blood test Follow the instructions from your GP or hospital about fasting and the timing of your test, as some tests only give accurate results under certain conditions. Let the staff know if you take blood-thinning medicines or have a history of fainting during blood tests. ## Understanding your blood test results Reference ranges vary between laboratories and with your age, so results are always read in context. Mild abnormalities often need a repeat test before any action is taken, and your GP will explain what your results mean. ## ! When to speak to a doctor about the blood tests Your GP orders blood tests and explains your results. Call **111** for urgent advice if you feel very unwell while awaiting results or are unsure what to do. ## Common questions about the blood tests Do blood tests hurt? You usually feel a brief sharp scratch as the needle goes in, and it is over within seconds. Some people get a little bruising afterwards, which soon fades. Do I need to fast before a blood test? Some tests, such as fasting glucose and lipid profiles, usually need 8 to 12 hours without food beforehand. Water is fine unless you are told otherwise, so follow the instructions you are given. How long do blood test results take? Many blood test results are available within two to five days. Some specialised tests take longer, and your GP surgery can tell you when to expect yours. What happens if my blood test results are abnormal? Your GP interprets the results in the context of your health and symptoms. Depending on what they find, they may repeat the test, start treatment, or refer you for further investigation. What free NHS health checks and screenings am I entitled to? Adults in England aged 40–74 are invited for a free NHS Health Check every five years (blood pressure, cholesterol, diabetes risk). Screening programmes include bowel cancer (home test kit), breast screening (mammogram), cervical screening (smear test), and abdominal aortic aneurysm screening for men at 65. You will normally be invited by letter — check with your GP if you think you have missed one. ## Sources - [NHS — Blood tests](https://www.nhs.uk/conditions/blood-tests/) - [NHS — NHS Health Check](https://www.nhs.uk/tests-and-treatments/nhs-health-check/)