Supplements, whether vitamins, minerals, or herbal remedies, are often marketed as safe, 'natural' ways to improve health. But when combined with prescription or Over-The-Counter (OTC) medicines, they can sometimes do more harm than good.
According to Dr Vineet Rao, Consultant - Internal Medicine, Jupiter Hospital, Pune, certain supplements can alter how your body processes drugs, which may lead to serious, even life-threatening, consequences.
How Do Supplements Interact With Medicines?
The body processes medicines through specific metabolic pathways, often involving the liver and digestive system. Some supplements can speed up these processes, causing medications to break down too quickly and become less effective. Others can slow or block the breakdown, leading to an accumulation of drugs in the body and increasing the risk of side effects.
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For instance, certain herbal supplements used for mood disorders can accelerate drug metabolism. “This could result in making certain medications like birth control pills, antidepressants, blood thinners, and several cancer treatments ineffective,” says Dr Rao.
A 2019 US survey published in the journal Nutrients found that nearly half of people taking certain common medicines, like antibiotics, blood pressure drugs, or diuretics, were also using supplements that could cause harmful interactions. Older adults and those with higher education were most at risk. The study urges doctors to ask about supplement use before prescribing, to help prevent these potentially serious mix-ups.
Common Examples Of Risky Interactions
Some well-known supplement–drug interactions include:
Vitamin K and blood thinners: Vitamin K can counteract the effects of warfarin, making it less effective. If you’re on blood thinners, you must consult your doctor before taking vitamin K supplements or changing your dietary intake of the vitamin.
Iron or calcium and thyroid medicines: These minerals can interfere with the absorption of levothyroxine, a common thyroid hormone replacement drug.
5 Key Things To Keep In Mind
Some of the things to consider before combining supplements with drugs include:
- Timing matters – if you must take both supplements and medicines, leave at least a two-hour gap between them to minimise interference.
- Always disclose your supplements – Let your doctor know about all supplements, herbal remedies, or over-the-counter products you use.
- Don’t assume “natural” means safe – natural products can still cause side effects or interact dangerously with medicines.
- Be wary of high doses – even essential nutrients can be harmful in excess.
- Watch for symptoms – if you start a new supplement and notice unusual side effects, inform your healthcare provider immediately.
Not Everything That Is ‘Natural’ Is Safe
One of the biggest misconceptions about supplements, Dr Rao notes, is that if something is 'natural', it must be safe. “That’s not always true,” he cautions. High doses can be harmful, and certain supplements can cause drug interactions or side effects.
Unlike prescription medicines, supplements are not regulated as strictly, so their potency and purity can vary widely between brands. This makes professional guidance even more important.
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Can Interactions Ever Be Positive?
While most supplement–drug interactions are seen as risks, some can be beneficial when managed under medical supervision. For example, certain supplements may enhance drug absorption or complement the medicine’s action. However, this should only be attempted under the guidance of a healthcare professional.
Safety Measures Before Starting A Supplement
If you’re on medication for any condition, start with your doctor’s advice before adding a supplement. Share your full medication list, doses, and medical history.
To protect yourself:
- Read labels carefully for dosage and ingredient details.
- Choose reputable brands that undergo third-party testing for quality.
- Avoid products with “miracle cure” claims, as these are often misleading.
- Start with a lower dose and monitor your body’s response.
Conclusion
Supplements can offer health benefits, but they are not risk-free, especially if you’re on medication. The safest path is to involve your healthcare provider in every decision, maintain transparency about what you’re taking, and be mindful of possible interactions.
Dr Rao cautions, “Many people are unaware that certain supplements can mix with prescription medicines or be contraindicated for specific medical conditions.” That’s why he advises sharing your complete list of medications and supplements with your doctor before starting anything new.