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Monitoring Your Medicines

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Topic Overview

You may wonder, "Why would I need to have tests to check on medicine that's meant to help me?" Your doctor may want you to have tests to be sure that the medicine isn't harming you and that you're getting the right dose. Sometimes the amount of medicine that helps you is very close to the amount that can cause harm to your body.

Monitoring your medicines helps you and your doctors to:

  • Be sure you are getting the right dose for your gender, age, and weight.
  • Be sure the medicine is working for you.
  • Avoid bad interactions with other medicines.
  • Avoid damage to your heart, kidneys, liver, or other organs.

Your doctor will likely let you know when you need to have the tests. If you think a medicine you're on should be monitored but you're not sure how long it's been since your last test, talk to your doctor. He or she can let you know if and when you need to be checked.

It's important to know how to prepare for the test, such as knowing when you took the last dose of the medicine for which you are being tested. Ask your doctor for instructions about the timing of the test.

Tell your doctor about all the prescription and nonprescription medicines you are taking and any drugs (such as alcohol, marijuana, or cocaine) you are using. Sometimes these can interfere with testing.

Common medicines that are monitored
Examples What they do Why monitor them Tests you may have How often

ACE inhibitors


These medicines lower blood pressure, treat heart failure, and help prevent heart attacks and strokes.

They may affect how well your kidneys are working and the level of potassium in your body.

At least once a year or as often as your doctor suggests

Angiotensin II receptor blockers


These medicines lower blood pressure and help treat heart failure.

They may affect how well your kidneys are working and the level of potassium in your body.

At least once a year or as often as your doctor suggests



These medicines help prevent or control seizures and help treat chronic pain.

It may take time and careful, controlled adjustments to find the right combination, schedule, and dose for you.

  • Blood test to check the drug level in your blood

At least once a year or as often as your doctor suggests


It helps control heart rate and helps make your heart beat stronger.

When you start taking this medicine, you may need to have frequent blood tests to monitor the level of the medicine in your body.

If your kidneys aren't working properly, the medicine can build up to a dangerous level. Also, the level of potassium in your body may affect how the medicine works.

At least once a year or as often as your doctor suggests



These medicines reduce the fluid in the body and lower blood pressure.

They may affect how well your kidneys are working and the level of potassium in your body.

At least once a year or as often as your doctor suggests


It helps prevent blood clots. Because it prevents clots, it also helps prevent heart attacks, strokes, and other problems caused by blood clots.

Things like an infection or a small change in your diet can change the way warfarin works. So can other medicines that you are taking.

As often as your doctor suggests


WebMD Medical Reference from Healthwise

Last Updated: September 09, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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