Your blood is a wealth of information and can tell you a lot about your internal health. You might do a blood test as part of a regular check-up or it can be used to help diagnose an illness or genetic condition. Some of the things you test for require a venous blood sample (from your arm). But in some cases, it’s possible to do a less invasive finger-prick blood test.
- What can a blood test show?
- How to do a blood test
- Where to get a blood test
- Do blood tests hurt?
- Preparing for a blood test
- Fasting before a blood test
- How long does it take to get blood test results?
- What to expect from your blood test results
What can a blood test show?
Your blood can tell you a lot about your health. You might do a blood test to check:
- your vitamin and mineral levels — like your vitamin B12 or iron levels
- your cholesterol levels
- how well certain organs are functioning — like your liver and kidneys
- your thyroid function
- your blood sugar levels and your risk of diabetes
- for an infection
- for any genetic conditions
As well as giving you a snapshot of your current health, you can use a blood test to keep track of your risk of long-term chronic diseases like heart disease and diabetes.
How to do a blood test
There are two main ways to collect a blood sample, either using a venous or finger-prick method. This is what to expect from each type of blood test:
- a venous blood test — a needle is used to puncture a vein, usually in your arm, and allows you to collect a large blood sample. This type of blood test can be used to test a full-range of biomarkers but is more invasive.
- a finger-prick blood test — a lancet is used to prick your finger and allows you to collect a small blood sample. You can do this type of test yourself and it’s less invasive than a venous sample. However, while it can be used to test a wide range of biomarkers it’s not possible to test every biomarker.
Where to get a blood test
NHS blood tests
One of the many services that the NHS provide is blood testing. This can be done at your GP’s or a local hospital. A trained nurse or doctor will take your blood, usually a venous sample and it will be sent to the lab to be analysed.
Private blood tests
This can be done through a health professional or you can order a blood test online and do it yourself at home. For at-home tests, the same accredited labs and methods are used to test your sample as the NHS.
Do blood tests hurt?
It’s normal to be nervous about doing a blood test — it’s human nature not to like pricking yourself with a needle or looking at your own blood! But the process is very straightforward and while it might feel a little uncomfortable it won’t be painful.
Venous blood test
With a venous blood test, all you’re likely to feel is a little pinch when the needle goes in, the blood being drawn out won’t hurt at all. You might have a small bruise where the needle went in.
Finger-prick blood test
As the name suggests, all you’ll feel is a small prick on your finger. The area the lancet went in might be a little tender afterwards.
Preparing for a blood test
There are a couple of things you can do before a blood test so the process is as smooth as possible:
- drink a lot of water — being hydrated makes it easier to collect your blood sample
- stay warm — having a hot shower or jumping on the spot for a minute makes it easier to collect your blood sample (especially for finger-prick samples)
For some tests, you might need to stop taking certain medications. But you should only do this if your doctor has told you. You might also need to fast before a blood test.
Fasting before a blood test
Fasting means not eating or drinking anything except water for up to 8-12 hours before your test.
This is because when food and drinks are broken down and absorbed into your blood it can affect your results — for example, having a high-fat meal right before a lipid test could cause your triglycerides levels to look higher than they actually are.
Blood tests that usually require you to fast include a:
- lipid profile (cholesterol and triglycerides) test
- blood sugar (glucose) level test
- fasting insulin test
- liver and kidney function test
- iron test
- vitamin B12 test
How long does it take to get blood test results?
Your results can take anything from one day to a few weeks to come in.
If you’ve done your blood test through the NHS or a private specialist, your results will be given to them to interpret and share with you. If you did your blood test at home, your results will also be interpreted by a doctor and then uploaded online where you can view them.
What to expect from your blood test results
For many tests, your blood will be analysed to measure the levels of a certain compound, enzyme, or antibody that might be present. This will be compared to a reference range to see if it’s within the normal range. These reference ranges can vary depending on your age, gender, ethnicity, and family history.
Along with reference ranges, all of the abbreviations and various units of measurements included in your blood test results can make it difficult to understand them. So it’s important to have a doctor or a health professional review and interpret your results for you.
National Health Services (2018). Overview: Blood tests. Retrieved 9 November 2018 from https://www.nhs.uk/conditions/vitamins-and-minerals/.