Why Regular Blood Tests Matter: What They Check and How Often

In short: Blood tests can show how well your organs are working, pick up problems such as anaemia, raised cholesterol, diabetes or thyroid disease before symptoms appear, and help monitor long-term conditions and medicines. How often you need them depends on your age, health, family history and any treatment you take. Results should always be interpreted by a qualified clinician alongside your symptoms and history.

This guide, written by a Ready Health prescribing pharmacist, explains what routine blood tests check, who may benefit from regular testing and what to expect on the day.

Why are regular blood tests important?

Many common conditions develop silently. Regular blood tests can help to:

• identify risk factors early, such as raised cholesterol or blood sugar, when lifestyle changes or treatment can make a difference
• find treatable causes of symptoms like tiredness, for example low iron, low vitamin D or low vitamin B12
• monitor long-term conditions such as diabetes, kidney disease or thyroid disorders
• check that certain medicines are working and not causing side effects, for example some blood pressure tablets, statins, lithium, methotrexate or thyroid medicines
• give you a baseline to compare against in future

What do common blood tests check?

For HbA1c, UK guidance uses 48 mmol/mol or above to indicate diabetes, and 42 to 47 mmol/mol to indicate a raised risk (sometimes called prediabetes). Reference ranges for most other tests vary between laboratories, so results should be read against the range printed on your own report.

Can blood tests detect cancer?

Routine blood tests can sometimes show changes that prompt further investigation, such as unexplained anaemia. However, most cancers cannot be reliably screened for with a single blood test. Tests such as PSA for prostate cancer have benefits and limitations that should be discussed with a clinician before testing. Always follow the NHS screening programmes you are invited to, and see your GP about any persistent or worrying symptoms.

How often should I have a blood test?

There is no single answer. As a general guide:

• Adults aged 40 to 74 in England without certain existing conditions should be invited for a free NHS Health Check every 5 years, which includes a cholesterol test and may include a blood sugar test.
• People with long-term conditions or on medicines that need monitoring will usually have tests at intervals set by their care team, often every 3 to 12 months.
• People with symptoms, such as persistent tiredness, unexplained weight change or excessive thirst, should speak to a clinician, who can decide which tests are appropriate.
• A private health check may suit people who want a more detailed picture or more flexible timing. Read more in how often you should have a check-up.

How should I prepare for a blood test?

• Follow any instructions you are given. Most tests do not need fasting, and cholesterol is usually tested without fasting in the UK, but some tests (such as fasting glucose) do.
• Drink water beforehand, as being well hydrated makes veins easier to find.
• Bring a list of your medicines and supplements. Biotin supplements, for example, can interfere with some test results.
• Wear a top with sleeves that roll up easily.
• Tell the person taking blood if you feel faint with needles or have a bleeding disorder or take anticoagulants.

What happens during a blood test?

A trained clinician or phlebotomist confirms your details, places a band around your upper arm, cleans the skin and takes a small sample from a vein, usually in the inside of your elbow. It takes a few minutes. Afterwards, press on the site for a minute or two. A small bruise is common and fades within days. Seek advice if you notice increasing pain, swelling or redness.

How are blood test results explained?

Results are reported as numbers alongside a reference range. A result slightly outside the range does not always mean something is wrong, and a normal result does not rule out every condition. Food, exercise, medicines, recent illness and the time of day can all affect results. A clinician should explain your results, decide whether repeat or further tests are needed, and refer you to your GP or a specialist where appropriate. Find out more about what private blood tests can tell you.

Frequently asked questions

Do I need to fast before a cholesterol test?

Usually not. UK practice is to check cholesterol without fasting unless your clinician advises otherwise, for example if triglycerides were very high previously.

Can I get a blood test without seeing my GP?

Yes. Private clinics offer blood tests, but it is important that results are reviewed by a qualified clinician and that anything significant is shared with your GP.

How long do blood test results take?

Many routine results are available within a few working days. Some specialist tests take longer.

Are home finger-prick tests as good as a blood draw?

Some tests work well with finger-prick samples, but others are less reliable or need a larger sample. A clinician can advise which method suits the tests you need.

Key takeaways

• Blood tests can detect risk factors and conditions early and help monitor treatment.
• Common tests include FBC, HbA1c, cholesterol, kidney, liver and thyroid function.
• How often you need testing depends on your age, health and medicines.
• Results should always be interpreted by a clinician.

Sources and further reading

• NHS: blood tests
• NHS: NHS Health Check
• NICE CKS: type 2 diabetes
• NHS: high cholesterol

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician.

Thinking about a blood test in Wigan, Standish, Chorley or Bolton? Find out more about blood tests at Ready Health. A clinician will discuss which tests are appropriate for you and explain your results.