Avoid Potential Danger: Mixing Medicines and Supplements

If you take natural dietary supplements to ease symptoms of menopause, depression or any other conditions, you could be changing the way medicines you take work inside your body.

Supplement and prescription medicine chemical interactions can be minor or dangerous. They can weaken your medications and make them less effective, or they might make your prescriptions more powerful.

When medicines and supplements combine with the foods and alcoholic beverages we consume, even more changes can occur.

How Supplements Work in the Body

More than a third of all Americans take some kind of dietary supplement in addition to prescription medicines, such as supplements for bone health and osteoarthritis, says the Centers for Disease Control and Prevention.

Unfortunately, there is not enough clinical evidence to know exactly how these supplements interact with all medicines, or with each other. That’s why mixing medicines and supplements is so scary.

We do know that some supplements change the way our bodies break down medicines. They can cause more of the medicine to be absorbed or excreted, changing its potency. If you’re getting too much or too little of the drugs your doctor prescribed, you could be in danger.

That’s why it’s important to tell your doctor about every supplement you use, including: 

  • Vitamins
  • Minerals
  • Herbal and botanical supplements
  • Amino acids
  • Enzymes

Also make sure your doctor knows about all medicines you take. Many medicines also interact with each other. Some work well together and some don’t.

Your doctor can determine the best combination of medicines and supplements for you, based on your diet and your specific condition.

If you’re getting too much or too little of the drugs your doctor prescribed, you could be in danger.

What Happens When Medicines and Supplements Interact

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Many substances can interact with prescription medicines and supplements. Here are some examples. 

  • Vitamins and minerals. Iron supplements can prevent some antibiotics from working properly.
  • St. John’s wort. This supplement speeds up how your body metabolizes medicines. This reduces the effectiveness of those medicines, including birth control pills and medicines for depression, heart disease, HIV/AIDS and organ transplant recipients. St. John’s wort may decrease the potency of 70 percent of all prescription medicines. 
  • Ginkgo biloba. This herbal supplement thins the blood. If you are taking a prescription blood thinner like warfarin, it could be dangerous. Aspirin and vitamin E also act as blood thinners and a combination of any of them could lead to stroke or internal bleeding.
  • Grapefruit juice. This drink can stop the body from being able to break down some medicines, which means they may stay in your body longer than intended.
  • Alcohol. All types of alcoholic drinks can cause interactions with more than 150 different medicines, says the National Institute on Alcohol Abuse and Alcoholism. Alcohol slows breathing and can be dangerous when combined with sedatives, sleeping pills and prescription painkillers. 

Studies have shown some evidence that the following supplements can interact with prescription drugs and interfere with how the body processes medicines: 

  • Concentrated garlic extracts (prolonged exposure)
  • Ginseng
  • Goldenseal
  • Kava

Tell your doctor if you are using these supplements along with prescription medicines so that you can be closely monitored.

Reasons to Worry: Exact Dosages and Surgery

Problems that result from taking supplements and medicines together can be especially dangerous if you’re going to have surgery or your prescription has a “narrow therapeutic range.”

Exact dosages. Some medicines require a very specific amount to work properly. If too little or too much of the drug will cause serious side effects, the medicine is known to have a narrow therapeutic range or index. That’s why it’s important to take your medicine as prescribed.

Supplements can increase or decrease the amount of medicine that stays in your body, regardless of the dosage you take.

Surgery. If you are scheduled for surgery, talk with your doctor about all of the supplements you use. Supplements can affect how your body responds to anesthesia and medicines you may need before, during and after surgery. Supplements can also increase your bleeding risk. Your doctor may ask you to stop taking supplements a few weeks before your surgery.

6 Safety Tips for Supplements and Medicine

While some vitamins and supplements can be good for you, others may be harmful. Remember that even if a product is labeled as “natural” it may be unsafe and it may contain hidden drug ingredients.

To prevent negative reactions from taking supplements, follow these tips:

  1. Tell all of your doctors about every medicine and supplement you take. Bring a list to your appointments.
  2. Tell your doctor about changes in your health status, such as a recent illness, being pregnant or a scheduled surgery.
  3. When you are prescribed a new medicine, ask your doctor these questions:
    • Can I take this with the other medicines I am using?
    • Should I avoid certain foods, beverages or other products?
    • What are possible drug interaction signs I should know about?
  4. How will the drug work in my body?
  5. Use a drug interaction checker. To find out about any possible interactions among medicines you take, enter your list of medicines at drugs.com or rxlist.com. If any interaction warnings appear, talk with your doctor before making any changes. 
  6. Read all labels on any over-the-counter and prescription medicines you take. 
  7. Use one pharmacy for all of your family’s prescriptions. This keeps all of your medications on record in one place and makes it easier to track medicines prescribed by different doctors. 

If you have a bad reaction while taking a medicine or supplement, report it to the FDA. You can:

Small Steps: Know Your Individual Triggers.
If you have asthma, ask your doctor about allergy testing to help you avoid triggering an unwanted attack.