Herbal supplements and medication interactions: bring everything you take

Picture someone on a blood thinner who drinks a herbal tea every night on a neighbor’s advice, or who adds a supplement “for immunity” two weeks before surgery. They feel fine, see no reason to mention it, and no one on their care team knows it exists. This is very common. In Puerto Rico many families carry a tradition of herbs, teas and home remedies handed from grandmother to grandchild, and today it sits beside a shelf of supplements from the pharmacy, the health-food store or the internet. Many people use these at the same time as prescribed medicines and never mention them, because they do not think of them as “medicine.”

To your body, though, an active plant is an active substance. It can raise or lower the effect of a medicine, add to an effect another one already has, or cause side effects of its own. Your doctor cannot assess a risk they do not know exists. Product strength varies from brand to brand and from one homemade tea to another, so this guide suggests no dose. A pharmacist can also check interactions, including with over-the-counter medicines.

This guide does not tell you what to take or stop taking. It explains why everything should be reviewed together, which situations call for extra care, and how to prepare the conversation.

NCCIH, the National Institutes of Health center that studies these practices, is blunt: “natural” does not always mean “safe.” Kava, for example, has been linked to liver disease.

Supplements are not approved to treat disease. A supplement label cannot claim that the product diagnoses, treats, cures or prevents a disease; only drugs can make those claims. Phrases like “supports healthy…” are something else and do not show that a product works.

They are watched less closely than drugs. FDA generally cannot review a supplement for safety or effectiveness before it is sold; it acts after problems appear. Some products sold as supplements have been found to contain prescription drugs that were not on the label.

None of this means every supplement is dangerous. It means “comes from a plant” is not a guarantee, and that dose, brand, your own conditions and what you already take all matter.

These are the situations where an interaction weighs most. In all of them the rule is the same: do not start, change or stop anything on your own; talk to a physician or pharmacist first.

Herbs and supplements are not all alike when it comes to evidence, which is why a blanket “it works” or “it’s useless” is almost never accurate.

Evidence varies product by product. NCCIH says St. John’s wort may help mild to moderate depression, and that it interacts with many medicines (see above). Depression needs a clinical assessment: do not start this product, or stop an antidepressant, on your own.

Often the evidence is limited or mixed. Small studies, short ones, or ones using different products cannot tell you whether a supplement will help you in particular. “More research is needed” is an honest answer.

Habits are the foundation. Sleep, movement, a varied way of eating, not smoking, little alcohol and stress management are well-established foundations of health. They are the core of lifestyle medicine and do not replace medical care.

If you already use a product and want to know what is known about it, that is a fair question for the physician. She can tell you honestly what the evidence supports and what it does not.

A good review starts before the appointment. These steps help:

Trying a remedy for weeks while a symptom continues has a cost: whatever is causing the symptom is still there. Ask for an assessment if a symptom does not improve, worsens, returns or changes, if you have a fever that will not settle, unexplained weight loss, unexplained tiredness, unusual bleeding or easy bruising, or if a product does not sit well with you.

If you have an adverse effect after a product (for example hives, swelling, vomiting, yellow eyes or skin, dark urine or strong dizziness), stop the herb or supplement (not a prescribed medicine) and contact your doctor or pharmacist; if you are not sure whether a prescription is the cause, call before stopping it. For chest pain, shortness of breath, swelling of the face or tongue, fainting, confusion, seizures, bleeding that will not stop or thoughts of harming yourself, call 911 or go to the emergency room.

If you feel you cannot go on or are thinking of harming yourself, call or text 988, or the Línea PAS at 1-800-981-0023. It is confidential.

The Health Initiative (THI) is the nonprofit that runs this telehealth clinic. Dr. Diana Nieves Castro is a general practice physician licensed in Puerto Rico. Her approach is integrative within medical care: a medical assessment first, then sleep, nutrition, movement and stress, and a review of everything you take.

In an online visit the physician can ask about everything you take, including supplements, herbs and teas, and take it into account in your assessment; she can also talk about what the evidence supports, ask for lab orders when needed and, when appropriate, receive a prescription. Afterward you can have a follow-up to review results or adjust the plan. Online visits are only for people who are physically in Puerto Rico.

The physician reviews what you take and what the evidence supports; THI does not sell products, so the review stays independent. She can help you decide what to bring to those visits and say clearly to every clinician what you take. Learn more about Dr. Nieves Castro. Separately, THI offers an in-person retreat, held in English; it is a different program, not part of a medication review or medical treatment.

This guide is general information. It is not a diagnosis, does not replace your doctor, and should not be used to stop, change or delay a medicine, vaccine or screening without first talking to a health professional.