Nursing care
Herbal Supplements, explained for the bedside and the exam
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Herbal supplements are not routinely disclosed by patients because most do not consider them medication, so nurses must ask about them directly and by name during medication reconciliation. Common supplements such as St John's Wort, ginkgo, garlic, and ginger interact with anticoagulants, antidepressants, and perioperative drugs. Missing this history is a preventable cause of adverse interactions.
What the concept actually says
A standard medication history asks "what medications are you taking" and most patients answer with their prescriptions and perhaps an over-the-counter analgesic. Herbal supplements are left out not because patients are hiding them, but because they file supplements under diet or wellness, not medication, and the question as asked does not prompt them to mention it.
This means a medication reconciliation that relies on an open-ended question will systematically miss herbal use. The concept requires the nurse to ask a separate, specific question: "are you taking any herbal supplements, vitamins, or products from a health food store?" The wording matters, because the goal is to trigger a different mental category than "medication" does.
The clinical reasoning behind it
Herbal supplements are pharmacologically active, and several have well-documented interactions. St John's Wort induces cytochrome P450 enzymes, reducing the effectiveness of warfarin, oral contraceptives, and some antidepressants, and can precipitate serotonin syndrome when combined with SSRIs. Ginkgo biloba, garlic, and ginger all have antiplatelet effects and increase bleeding risk when combined with anticoagulants or before surgery.
The reasoning is not that supplements are inherently dangerous, but that undisclosed use breaks the assumption a prescriber relies on when they check for interactions against the documented medication list. A warfarin dose that looks stable on paper can be masked or destabilised by a supplement nobody recorded. Asking directly closes that gap before it becomes a bleeding event or a failed treatment the prescriber cannot explain.
Applying it under time pressure
On a busy admission, the medication reconciliation question is easy to compress into a single "any other medications?" that gets a quick no. The discipline is to keep the herbal supplement question as its own line item, asked by name, even when time is short, because it is precisely the question patients will not volunteer an answer to unprompted.
Before any surgical procedure, ask specifically and document the answer, since several common supplements need to be stopped one to two weeks beforehand because of bleeding risk. If a patient reports an unexplained bleeding tendency, an unusual response to a psychiatric medication, or a drug level that does not match the prescribed dose, herbal use is worth asking about again even if it was checked at admission, because supplement use is often ongoing and not always mentioned once.
Common misconceptions
The most persistent misconception belongs to patients, not nurses: the belief that "natural" means "safe" and therefore not worth mentioning to a clinician. This is the exact belief that produces the underreporting the whole concept exists to counter, and it is worth naming to the patient directly rather than assuming they already understand supplements can interact with prescribed drugs.
A second misconception is that asking once at admission is sufficient. Supplement use changes, a patient may start something new mid-stay if a family member brings it in, and a single point-in-time check does not account for that. A third is assuming supplement use is limited to certain patient groups; it cuts across age, background, and health literacy, and should be asked of every patient, not selectively.
Practice scenarios
A patient on stable warfarin therapy is admitted with an INR far above therapeutic range with no dosage change and no new prescribed medication. The nurse asks specifically about herbal supplements and the patient discloses starting ginkgo biloba for memory two weeks earlier; the interaction, not a dosing error, explains the abnormal INR.
A pre-operative patient answers "no" to a general medication question but, when asked directly about herbal products, mentions taking garlic capsules daily for cholesterol. Because garlic has antiplatelet activity, the surgical team is notified and the supplement is held before the procedure. In both scenarios, the correct action is the direct, named question, not a general one, and documentation of the answer in the medication record so the rest of the care team has it.
Key takeaways
Herbal supplement use is underreported because patients do not classify it as medication, not because they are being evasive. The nursing response is a specific, direct question asked by name at every medication reconciliation, not folded into a general "any other medications" prompt.
Know the interactions that come up most often in practice: St John's Wort with antidepressants and warfarin, ginkgo and garlic with anticoagulants, and the general principle that antiplatelet-active herbs raise bleeding risk before surgery. Document what the patient reports, repeat the question when clinical findings do not add up, and treat a disclosed supplement with the same seriousness as a disclosed prescription.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pharmacology practice questions are the closest set to what this page covers.
One question from the pharmacology set
A client with heart failure is started on furosemide 40 mg PO daily. Which findings should the nurse report to the provider before administering the next dose? Select all that apply.
Rationale
Furosemide is a loop diuretic, so the two things you are watching are potassium and kidney function. A potassium of 2.9 mEq/L is below the 3.5–5.0 reference range and puts the client at risk for dysrhythmia — hold and report. Muscle cramps with palpitations are the clinical face of that same hypokalemia, so they are reported together, not separately. A creatinine that doubles signals the diuresis has outrun renal perfusion. A blood pressure of 132/78 and a 1 kg loss are the expected response to the drug working, not reasons to hold it.
Answer: A, D, E
Common questions
Why don't patients tell nurses they take herbal supplements?
Most patients do not consider herbal products to be medication, so a general question about medications does not prompt them to mention it. They are more likely to file supplement use under diet, wellness, or a family recommendation rather than something relevant to their clinical care.
Which herbal supplements interact with warfarin?
St John's Wort, ginkgo biloba, garlic, and ginger are the supplements most often implicated in warfarin interactions, either through altering drug metabolism or through their own antiplatelet or anticoagulant effects. Any patient on warfarin should be asked specifically about these by name, not just about supplement use in general.
When should herbal supplements be stopped before surgery?
Supplements with antiplatelet or anticoagulant effects, such as ginkgo, garlic, and ginger, are generally advised to stop one to two weeks before a surgical procedure because of bleeding risk. Exact timing should follow the surgical team's or anaesthesia provider's guidance, since it can vary by procedure and by the specific supplement.
How should a nurse phrase the question to get an honest answer about supplement use?
Ask specifically and by category: "are you taking any herbal supplements, vitamins, or anything from a health food store?" rather than a general "any other medications?" Naming the category is what prompts patients to recall something they otherwise would not think to mention.
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