Drug and medication monitoring

What is drug and medication monitoring?

Drug and medication monitoring means having regular blood tests while you're taking certain medicines, to check they're working safely at the right dose. For some medicines, this means measuring the amount of the medicine itself in your blood. For others, it means checking how your organs, such as your liver or kidneys, are coping with it.

Why might I need this?

You might need this if you're taking a medicine that has to stay within a particular level in your blood to work properly, since too little may not treat your condition and too much can be unsafe.

Other medicines still need regular blood tests to look for effects on organs such as your liver, kidneys or blood cells.

You may need monitoring when you first start a medicine, to find the right dose for you, and then regularly afterwards, especially if your health changes, you start another medicine, or you get older.

What are the benefits?

Regular monitoring means your doctor can catch problems early, such as a dose that's too low to work or high enough to cause side effects, and adjust your treatment before this becomes more serious.

For medicines like methotrexate or azathioprine, this means checking your kidney, liver and blood cell function stays healthy while you take them.

Are there different types of monitoring?

There are two main kinds:

• Measuring the level of the medicine itself in your blood: This is used for medicines such as certain antibiotics, heart medicines, anti-seizure medicines, lithium and some antifungal medicines, where the amount in your blood needs to stay within a specific range
• Checking your organs and blood cells for signs that a medicine is affecting them: This is used for medicines such as methotrexate, azathioprine and ciclosporin, where regular blood tests check your kidney, liver and blood cell function.

How do I prepare?

Depending on the medicine you're taking, you may need to schedule your blood test for a particular time before or after your dose. Tell your provider about any other medicines or supplements you take too, as these can affect the results.

If you're on a stable dose of a medicine like methotrexate or azathioprine, blood tests are usually needed every 3 months, with more frequent tests when you first start treatment.

What happens during the test?

A healthcare professional takes a small blood sample from a vein in your arm using a needle. You may feel a brief sting as the needle goes in, and the sample usually takes less than 5 minutes to collect.

What happens after the test?

Your results are checked against a 'therapeutic range', the level considered both effective and safe for that particular medicine. If your levels are outside this range, your doctor may need to adjust your dose, and you may need repeated tests until your levels settle into the right range.

If you take a medicine like methotrexate or azathioprine, your prescription may only be renewed once your blood test results have been reviewed by a clinician. If a test is overdue, your medicine may temporarily disappear from your repeat prescription list. This doesn't mean it's been stopped, it just means it's waiting for this review.

What are the risks?

Having a blood test carries very little risk. You might have slight pain or bruising where the needle went in, but this usually goes away quickly.

If a blood test is missed or delayed, your prescription may be delayed until the result has been checked, which is why it helps to keep up with your test appointments.