Supplements and Medications: What to Check Before You Start

Please read first: this article is general educational information. It is not medical advice, and it cannot account for your medication list, your health conditions, or your history. Talk to your doctor or pharmacist before starting, stopping, or combining any supplement with prescription medication. Do not change how you take a prescribed medicine based on anything you read here.

Start here before you start anything

If you take prescription medication, the single most useful thing you can do is bring your supplement list to your pharmacist. Pharmacists check interactions for a living, they are usually free to talk to, and they will give you a straighter answer than any article will. What follows is meant to help you ask better questions, not to replace that conversation.

We sell herbal extracts. It would be commercially easier to leave this page unwritten. We think a customer who knows when not to take something is worth more than one who does not.

Why herbs interact with drugs at all

Herbs are biologically active, which is the entire reason anyone takes them. The same property that makes a plant preparation worth using is what allows it to interfere with a medication. There is no version of this where something is potent enough to help but too inert to matter.

Interactions generally happen in one of three ways. The most common is simply additive: the herb and the drug push in the same direction, so the combined effect lands harder than intended. The second is metabolic. Many drugs are broken down by liver enzymes, particularly the cytochrome P450 family, and some plant compounds speed those enzymes up or slow them down, which changes how much drug ends up in your bloodstream. St John's wort is the best-documented example and affects a strikingly wide range of medications. The third is absorption, where a compound changes how much of a drug makes it out of your gut.

That last mechanism is one reason we do not add piperine, the black pepper extract, to our turmeric. Piperine is widely used to boost curcumin absorption and it genuinely works. It also affects the absorption and metabolism of other things you might be taking. We use fat pairing and whole-root extraction to handle absorption instead, which we explain in our piece on black pepper and turmeric.

Blood thinners and antiplatelet medication

This is the category that comes up most. Warfarin, clopidogrel, apixaban and even regular aspirin all reduce clotting, and several common botanicals appear to do so mildly as well. Turmeric and curcumin, ginger, ginkgo, garlic and high-dose fish oil are the names that recur.

Culinary amounts are not the concern here. Concentrated daily supplements taken alongside an anticoagulant are worth clearing with your prescriber, and especially so before any surgery or dental work.

Diabetes and blood pressure medication

Several botanicals have been studied for effects on blood glucose. If you already take medication that lowers blood sugar, adding something that pushes the same direction can stack in ways you did not plan for. This does not mean you cannot take them; it means your prescriber should know, and you should be monitoring.

Blood pressure follows the same logic. Anything with a mild blood-pressure-lowering effect, combined with a drug designed to lower blood pressure, can go further than intended.

Thyroid medication

Levothyroxine absorption is notoriously sensitive. Minerals in particular, magnesium and calcium and iron among them, can reduce how much is absorbed if taken at the same time. The standard guidance is to separate them by at least four hours. This is a timing problem rather than a prohibition, and it is easily solved once you know about it. Confirm the spacing with your pharmacist rather than guessing.

Sedatives, antidepressants and immunosuppressants

Calming botanicals combined with prescription sedatives can be additive, so if you take a benzodiazepine, a Z-drug or a sedating antidepressant, be cautious with anything marketed for relaxation or sleep.

With antidepressants the serious concern is serotonin syndrome, which is rare but genuine. St John's wort is the main botanical of concern and also affects the metabolism of many other drugs. If you take an SSRI, SNRI or MAOI, treat any mood-related supplement as a conversation with your prescriber rather than a self-directed decision.

And anyone on immunosuppressant therapy, whether after a transplant or for an autoimmune condition, should be careful with supplements marketed for immune support. Several functional mushrooms are studied for immune signalling, which is precisely the system the medication is deliberately suppressing.

Situations that deserve extra caution

Pregnancy and nursing come first, because most herbal supplements have never been studied in either. Absence of reported harm is not evidence of safety, and the reasonable default is to avoid them unless your obstetric provider says otherwise.

Before surgery, surgeons and anaesthetists generally want supplements stopped one to two weeks ahead, mostly because of bleeding risk. Tell them everything, including whatever you consider trivial. Kidney or liver disease changes the calculation for almost everything, since both organs handle clearance. Children are not small adults and pediatric dosing is not a scaled-down adult dose, so that is a question for a paediatrician. And autoimmune conditions deserve a conversation about immune-modulating supplements even without immunosuppressant medication in the picture.

How to actually check

Ask your pharmacist first, and bring the actual bottles or photographs of the labels so they can screen everything at once. Tell your prescriber too, because roughly half of supplement users never mention it, which removes information their doctor needs to treat them properly.

Beyond that, the NIH Office of Dietary Supplements fact sheets and the NCCIH herb pages are free, current and not selling anything. Start one thing at a time, so that if something feels off you know what to remove. And keep a written list with doses on it, and take it to appointments.

What honest uncertainty looks like

For many herb and drug pairs, the truthful answer is that nobody knows. A lot of what circulates as interaction information comes from laboratory studies, single case reports or theoretical mechanisms rather than clinical trials.

That cuts both ways. Some widely repeated warnings are weaker than they sound. Some real interactions have never been characterised because nobody funded the study. Which is a good reason to involve a pharmacist who can weigh the evidence for your specific situation, and a good reason to be sceptical of any supplement company, this one included, that tells you its products are risk-free for everybody.

Frequently asked questions

Can I take turmeric with blood thinners? Ask your prescriber before you do. Curcumin has been observed to affect platelet function, and combining it with an anticoagulant may increase bleeding risk. Culinary amounts in food are a different matter from a concentrated daily supplement. This is not a decision to make on your own.

Does lion's mane interact with medications? There is no well-established clinical interaction, but laboratory work suggests possible effects on platelet aggregation and blood sugar. If you take anticoagulants, diabetes medication or immunosuppressants, check with your doctor or pharmacist first.

Can I take magnesium with my thyroid medication? Often yes, but not at the same time of day. Minerals can reduce levothyroxine absorption, and separating them by at least four hours is the standard recommendation. Confirm the timing with your pharmacist.

Should I stop supplements before surgery? Generally yes, but let your surgical team make that call. Most ask for supplements to be stopped one to two weeks beforehand, mainly because of bleeding risk. Tell them what you take rather than deciding on your own.

Are herbal supplements safe during pregnancy? Most have not been studied in pregnancy, so safety is unknown rather than established. The reasonable default is to avoid them unless your obstetric provider specifically approves.

Who is the best person to ask about interactions? A pharmacist. They specialise in exactly this, they can screen your whole list at once, and the conversation is usually free.

Sources

National Institutes of Health, Office of Dietary Supplements. Dietary Supplements: What You Need to Know.

National Center for Complementary and Integrative Health. Herb-Drug Interactions.

National Center for Complementary and Integrative Health. St John's Wort and Depression: In Depth.

National Institutes of Health, Office of Dietary Supplements. Magnesium Fact Sheet for Health Professionals.

US Food and Drug Administration. Mixing Medications and Dietary Supplements Can Endanger Your Health.

This article is general educational information and is not medical advice. It is not a substitute for diagnosis or treatment by a qualified healthcare professional. Always consult your physician or pharmacist about your specific medications and health conditions before making any change. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.