Drugs may interact with herbs, and even vitamins and minerals, causing adverse reactions. The first step in avoiding is to know where the risks are.

Are you at risk?

If you take both dietary supplements and medicines, then there is a risk of drug-supplement interaction. However the very young, and the very old, run a greater risk for physiological reasons. Particularly heavy use of medication, and regular supplementation, also increases the risk. Therefore the need for precaution is especially important for elderly people, pregnant women and those who may become pregnant, nursing mothers, and people with chronic health problems.

Dietary supplements can interact with both prescription medicines and over-the-counter drugs such as aspirin and cold remedies. Many drug-supplement interactions reported in the medical literature have involved herbal supplements, such as licorice, and St. John's Wort. However, the problem of drug-supplement interactions is not limited to herbs. Vitamin E, folic acid, calcium, and zinc, are also known to interact with certain types of drugs.

How can drugs and supplements interact?

There are three main ways in which a supplement can :

1. A supplement may strengthen the effects of your medication. If both a supplement and a drug have similar actions in the body, then taking both together can cause an excessively strong effect. In this case, the supplement dosage should be limited to avoid interactions. To take an extreme example, combining an anticoagulant drug such as warfarin with a supplement that also inhibits blood coagulation, such as fish oil, could increase the risk of abnormal bleeding.

2. A supplement may reduce the bioavailability of your medication. A drug can either alter the breakdown of a supplement in your body, or prevent proper absorption of a supplement into your blood. Both of these effects will reduce the bioavailability of the supplement in your body, and so lower potency. Therefore it is best to increase the dosage of a supplement in these circumstances.

3. A supplement may seriously interact with your medication. Potentially the most dangerous type of interaction, sometimes a supplement has an excessively strong reaction with a drug, causing either adverse side-effects or drug overdose type symptoms. Where this is a concern, it is strongly recommended to avoid these supplements completely.

Taking control: how to avoid drug-supplement interactions

Despite the risks, there is no reason you should stop supplementing your diet, or taking your medication. All that is needed to avoid drug-supplement interactions is awareness and consultation with leading authorities on nutritional health before you start. is a professional online resource for anyone who wants to know more about vitamins, natural herbs, and other supplements. Our drug checker uses a comprehensive database of 6000 interactions to avoid harmful drug-vitamin interactions.