Can I take medication before having a blood test?

It depends on the type of blood test you’re having and what medication you take.

In some cases you can carry on taking your medicine before having a blood test, and in some cases you can’t. If you’re not sure or you have any questions about your blood test, ask your healthcare professional for advice.

Medication and blood test results

Some medicines can affect the results of a blood test, but this doesn’t necessarily mean that you need to stop taking your medicine.

For example, oral corticosteroids can increase your cholesterol levels in a blood cholesterol test. However, your GP or the healthcare professional who arranged the test can take this into account when interpreting your test results, so you won’t need to stop taking your medicine.

If you’re unsure, carry on taking your medicine as prescribed and check with your healthcare professional. You may also want to take your medicine with you to show the person carrying out the blood test.

Herbal remedies, vitamins or supplements can also affect results, so if you take any of these you should tell the GP or health professional who is arranging the test.

When to stop taking a medicine

You should never stop taking prescribed medication, unless you’re advised to do so by your GP or the healthcare professional responsible for your care. However, in some cases, you may need to stop taking a medicine before a blood test.

For example, if you're having an amylase test for pancreatic enzyme deficiency, some medication may cause your amylase levels to rise. These include corticosteroids, indomethacin and opiates (such as morphine and codeine).

Medication for the condition being tested

If you’re having a blood test to check whether your medication is working, in most cases you should carry on taking your medicine. For example, if you’re taking medicine to lower your cholesterol level, you should keep taking it before your cholesterol blood test, as the result will show whether the medicine is working.

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