In the summer of 2006, pharmacists at a university hospital in Kansas went back through the records of every patient who had passed through the anesthesia pre-operative evaluation clinic. There were 434 of them. The clinic’s own counseling sheet told patients to stop natural products 14 days before surgery. The records showed that patients arrived at the clinic, on average, 6.235 days before their operations.
Read those two numbers next to each other and the usual version of this topic falls apart. The useful question is who tells the patient, and when. By the time most people reach the appointment where the subject finally comes up, the interval printed on the handout has already expired.
The pharmacists published what they found in BMC Complementary and Alternative Medicine in 2009. Their conclusion was that if a surgeon does not raise discontinuation at least two weeks before the procedure, it may be too late to raise it by the time the patient is seen in the clinic.
What follows reports what professional guidance says, who says it and when it was written. It is not a schedule and not a recommendation. Decisions about what a specific person takes before a specific operation belong to that person’s surgeon and anesthesia team, who know the procedure, the bleeding risk and the rest of the medication list. The honest finding is that the published guidance is older, thinner and more internally inconsistent than its confident tone suggests.
The arithmetic of the pre-operative appointment
The Kansas review is worth understanding in detail, because it is the only study found that measured both sides of the problem: what patients were taking, and how much time was left to do anything about it.
Of the 434 patients who came through the clinic between July and August 2006, 104 reported currently using a natural product. That is 23 percent, roughly one in four. Most users, 58 percent, reported only one product. Only eight patients reported more than four.
The users were not a random slice of the surgical population. They were significantly older, averaging 62 years against 51 for non-users. They were more than twice as likely to be scheduled for cardiac or chest surgery, 17 percent against 7 percent. They were taking significantly more prescription medicines and more non-prescription medicines than non-users. In other words, the patients most likely to be taking a supplement were also the patients with the most complicated operations and the longest drug lists.
Mean time from clinic visit to surgery was 6.235 days, with a standard deviation of about seven days. Most appointments in that clinic were scheduled one week before surgery. The counseling form said 14 days. The gap was structural, not accidental: it was built into how the clinic was scheduled.
This is the single most actionable finding in the subject, and it points somewhere unexpected. The moment that matters is the day the operation is booked, not the pre-operative visit. That is the only point in the sequence where two weeks is still available.
The most-used product is not on the famous list
When the Kansas team sorted the 104 users by product, the result did not match the literature.
Fish oil came first, reported by 56 patients, 54 percent of users. Then glucosamine at 21 percent, garlic at 11 percent, flax seed at 10 percent, coenzyme Q-10 at 9 percent, saw palmetto at 6 percent, ginseng at 5 percent, and chondroitin, milk thistle and green tea at 4 percent each.
Now set that against the list that dominates the perioperative literature. In 2001, Michael Ang-Lee, Jonathan Moss and Chun-Su Yuan published a review in JAMA that searched the literature on 16 commonly used herbal medicines and selected eight for which safety information relevant to the perioperative period existed: echinacea, ephedra, garlic, ginkgo, ginseng, kava, St John’s wort and valerian.
Two lists, two agents in common. Garlic and ginseng appear on both. The most-used product in a real pre-operative clinic, fish oil, is not on the reviewed list at all, and neither is glucosamine, chondroitin, saw palmetto or coenzyme Q-10. The best-studied agents and the most-used agents are nearly different sets. Article 336 covers omega-3 products in their own right.
An earlier survey at a large Boston teaching hospital, published by L. C. Tsen and colleagues in Anesthesiology in 2000, split the question differently and found something else. Across an 11-week questionnaire of everyone attending the pre-operative clinic, 22 percent reported using herbal remedies and 51 percent reported using vitamins. Women and patients aged 40 to 60 were more likely to use herbal medicines. The most common herbal compounds, highest to lowest, were echinacea, ginkgo biloba, St John’s wort, garlic and ginseng. Vitamins were more than twice as common as herbs, and almost all of the perioperative literature is about the herbs.
Where the interval numbers come from
Here is the part that deserves care, because the provenance of the famous interval table is messier than its reproduction everywhere suggests.
The 2009 Kansas paper prints an eight-agent chart under the heading Original Chart in APEC. APEC is the clinic. The chart was posted in two of the clinic’s three patient rooms, and the paper’s authors say plainly that it was not complete or accurate and gave no references. They reproduced it to document the problem, not to endorse it.
Its agents are the same eight as the 2001 JAMA review, and the table is widely attributed to that review. That attribution could not be confirmed at the source in this work. JAMA’s full text sits behind a paywall and the published abstract of the 2001 review contains no discontinuation intervals at all. So the intervals below are reported for what they verifiably are: the contents of an unreferenced chart that hung on a clinic wall, which a later peer-reviewed paper reproduced while criticizing it.
The chart’s stated intervals, verbatim: ephedra, at least 24 hours before surgery. Kava, at least 24 hours. Ginkgo, at least 36 hours. St John’s wort, at least 5 days. Garlic, at least 7 days. Ginseng, at least 7 days. Echinacea, no data. The valerian row is cut off in the retrieved text, so no valerian figure is stated here.
Printing those numbers is reporting what a document said in a particular place at a particular time. It is not a schedule for anybody. Notice, too, that the range runs from one day to one week, which is the first clue that there is no single answer being approximated.
Three numbers for garlic, two for ginseng
The same 2009 paper also built its own table, headed evidence-based recommendations, and that table records the conflicts rather than hiding them.
Garlic is given as one week and as at least two weeks, two different figures in a single cell with different citations behind each. Ginseng is given as at least seven days and as at least two weeks. Fish oil, glucosamine, saw palmetto, chondroitin and milk thistle are each given 2 to 3 weeks. Flax seed, coenzyme Q-10 and green tea are each given no specific recommendations.
Add a third source and the spread widens again. A 2002 review in the Hong Kong Medical Journal by B Cheng, CT Hung and W Chiu assigned St John’s wort a two-week interval, against the clinic chart’s five days, and concluded that if in doubt a herbal medicine should be stopped two weeks before anesthesia and surgery.
Tally the published figures for a single agent and the picture is clear. Garlic: one week, or at least two weeks. Ginseng: at least seven days, or at least two weeks. St John’s wort: at least five days, or two weeks. For several widely used products, including the two most common ones after fish oil, the published answer is that there is no specific recommendation. A patient searching for a confident number will find one, and will find a different confident number on the next page.
No professional body has graded this
The absence at the center of the subject is a graded recommendation. In evidence-based medicine, a graded recommendation tells you how strong the underlying evidence is, usually with a letter. No letter grade for a supplement discontinuation interval was located in this work.
The Kansas authors wrote something striking in 2009: that the American Society of Anesthesiologists, while having no official statement on the question, nonetheless recommended discontinuing all natural products two to three weeks before elective surgery. Fifteen years later, a 2024 review in the Journal of Clinical Anesthesia by Ofelia Loani Elvir Lazo, Paul White and colleagues at Cedars-Sinai attributed to both that society and the American Association of Nurse Anesthetists a recommendation to stop herbal medications one to two weeks before elective surgery. Two peer-reviewed reviews, fifteen years apart, attribute two different intervals to the same body, and the earlier one says that body has no official statement. Neither society’s own document could be opened for this article, so both figures are reported as those reviewers characterize them, not as retrieved society positions.
Where a true guideline body has addressed bleeding risk around anesthesia, it has been candid about its evidence. The American Society of Regional Anesthesia and Pain Medicine publishes evidence-based guidelines on regional anesthesia in patients receiving antithrombotic or thrombolytic therapy. Its third edition, led by Terese Horlocker of the Mayo Clinic and published in Regional Anesthesia and Pain Medicine in 2010, is indexed under the subject headings for herbal preparations, so it addresses the category. On the strength of the evidence it is unusually direct: “the rarity of spinal hematoma defies a prospective randomized study, and there is no current laboratory model.”
One detail links the two documents and is easy to miss. Chun-Su Yuan, the third author of the 2001 JAMA review, also sat on the panels behind the regional anesthesia consensus statements. The same small group of researchers produced both the agent-specific intervals and the guideline that declines to put a grade on them. This is a narrow field, and that narrowness is part of why the numbers have not been revisited.
That single sentence explains the whole state of the field. The outcome everyone is trying to prevent is too rare to run a trial on. So the recommendations rest, as that document says of itself, on case reports, clinical series, pharmacology, hematology and the collective experience of recognized experts. That is a legitimate basis for caution. It is not a basis for a precise number of days.
What the anesthesia concern is
Set aside the intervals and the underlying worries are specific and plausible. The 2001 JAMA review grouped them. Direct effects included bleeding from garlic, ginkgo and ginseng, cardiovascular instability from ephedra, and low blood sugar from ginseng. Pharmacodynamic effects, meaning two things acting on the body in the same direction, included kava and valerian deepening the sedative effect of anesthetics. Pharmacokinetic effects, meaning a change in how the body handles a drug, included St John’s wort speeding up the metabolism of many drugs used around surgery.
The 2024 Cedars-Sinai review organizes the same territory by body system: coagulation, including raised bleeding risk; cardiovascular, including arrhythmias and both high and low blood pressure; central nervous system, including sedation, confusion and seizures; pulmonary, including coughing and bronchospasm; renal, including increased urine output; and endocrine and metabolic, including liver dysfunction and altered metabolism of anesthetic drugs. Article 353 covers how interactions work mechanically, and article 677 carries the interaction list itself.
Two of those deserve dating. Ephedra carries the most alarming entry on the old chart, including risk of heart attack and stroke and dangerous interactions with a class of older antidepressants. It is also conspicuously absent from the Kansas clinic’s product list in 2006, and the 2024 review does not name it among the herbal products most used before surgery. The hazard this literature cites most is not a description of what most people are taking now. And St John’s wort has an unresolved inconsistency attached to it: its documented enzyme-induction effect predicts faster clearance of many drugs, which is the opposite of the claim, sometimes repeated in patient materials, that it prolongs the effects of anesthesia. Both cannot be right in the same direction.
The federal government’s plainest statement on the subject comes from the NIH Office of Dietary Supplements, in its general consumer fact sheet rather than anything surgery-specific: “Some supplements can increase the risk of bleeding or, if taken before surgery, can change your response to anesthesia.” The same page advises keeping a complete record of supplements and medicines taken, and discussing them with a provider before any surgical procedure. Article 359 covers what that record should contain.
Nobody knows how often this causes harm
Here is the limit of what can honestly be claimed. No registry, case series or dataset quantifying perioperative adverse events attributable to dietary supplements was found. Individual case reports exist in the literature. A rate does not.
That absence matters in both directions. It means nobody can tell a patient the odds, and it also means nobody can dismiss the concern by pointing to a reassuring denominator, because there is no denominator.
The closest thing to national surveillance is not perioperative at all. A 2015 New England Journal of Medicine paper, written jointly by CDC and FDA staff, estimated the yearly national burden of supplement-related emergency visits using surveillance at 63 hospitals across 2004 through 2013. Article 359 carries those figures. They establish that supplements send a measurable number of Americans to emergency rooms every year. They say nothing about surgery, because there is no surgical denominator anywhere in that design, and the surveillance window closed in 2013. Treating an emergency department estimate as a perioperative event rate would turn one real finding into a fabricated one.
Clinician knowledge is the other half of the gap, and the Kansas paper reports it unflatteringly. Citing earlier work by Heller and colleagues, it notes that physicians correctly knew the side effects of only one natural product, ephedra, and did not recommend stopping 85 percent of natural products in the perioperative period. In a separate study, family medicine residents asked to match an herbal product to a drug interaction scored a mean of 32 percent. If a patient does raise the subject, the answer may be improvised.
Why it goes unmentioned, and the moment that matters
The 2024 Cedars-Sinai review reports that 50 to 70 percent of surgical patients do not disclose their use of herbal medications to their physicians, and that most do not discontinue them before surgery either.
National survey work on why patients stay quiet, which article 359 reports in detail, points away from the explanation most clinicians assume. Embarrassment and fear of disapproval are near the bottom of the list. The leading reasons are that the subject did not seem relevant to the doctor and that nobody asked.
Applied to surgery, that finding has an edge the general version lacks. A patient who does not think a fish oil capsule counts as medicine has no reason to mention it, and a booking conversation that covers allergies and fasting but never covers supplements does not give them one. The same 2009 Kansas paper notes that the clinic’s own interviews were mostly conducted by pharmacy students rotating through for a month, with the patient as the source of information in 89 percent of cases. Whether the subject comes up at all depends on whether a specific person on a specific day thought to raise it.
A short list of things worth raising with a surgical team, timed to when the operation is scheduled rather than to the pre-operative visit:
- Everything currently taken, including fish oil, glucosamine, vitamins and anything bought without a prescription, by name and amount.
- Whether this particular procedure carries a bleeding risk that makes any of it relevant, since the concern is procedure-specific rather than universal.
- Whether the surgeon or the anesthesia team is the one making the call, and how to reach whoever that is.
- What to do about anything taken for a diagnosed condition, since the decision there is a clinical trade-off rather than a precaution.
- Whether there is a written instruction, and what date it starts from.
The one thing worth carrying away is a correction to the premise. There is no authoritative stop list with agreed dates behind it. There is a twenty-five-year-old agent-specific chart whose own reproducers called it inaccurate, a set of conflicting intervals ranging from 24 hours to three weeks, a professional society whose position two peer-reviewed reviews describe differently, and a guideline body that says the outcome is too rare to study properly. What exists instead is a conversation, and it has to happen early enough to matter. The booking call is early enough. The pre-operative appointment, six days out on average, usually is not.
Sources
- Kennedy AR, Roberts FS, Grauer DW, Gruenbaum JA (University of Kansas). “"Evaluation and implications of natural product use in preoperative patients: a retrospective review." BMC Complementary and Alternative Medicine 2009;9:38. PubMed PMID 19825176; PMC2770030. Full text, including Tables 1 and 3, retrieved via the PubMed full-text tool. DOI: 10.1186/1472-6882-9-38.” pubmed.ncbi.nlm.nih.gov
- Ang-Lee MK, Moss J, Yuan CS (University of Chicago). “"Herbal medicines and perioperative care." JAMA 2001;286(2):208-216. PubMed PMID 11448284. DOI: 10.1001/jama.286.2.208. Abstract retrieved; full text paywalled..” pubmed.ncbi.nlm.nih.gov
- Elvir Lazo OL, White PF, Lee C, Cruz Eng H, Matin JM, Lin C, Del Cid F, Yumul R (Cedars-Sinai Medical Center). “"Use of herbal medication in the perioperative period: Potential adverse drug interactions." Journal of Clinical Anesthesia 2024;95:111473. PubMed PMID 38613937. DOI: 10.1016/j.jclinane.2024.111473.” pubmed.ncbi.nlm.nih.gov
- Tsen LC, Segal S, Pothier M, Bader AM (Brigham and Women's Hospital, Harvard Medical School). “"Alternative medicine use in presurgical patients." Anesthesiology 2000;93(1):148-151. PubMed PMID 10861158. DOI: 10.1097/00000542-200007000-00025.” pubmed.ncbi.nlm.nih.gov
- American Society of Regional Anesthesia and Pain Medicine (Horlocker TT, Wedel DJ, Rowlingson JC, et al.). “"Regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy: American Society of Regional Anesthesia and Pain Medicine Evidence-Based Guidelines (Third Edition)." Reg Anesth Pain Med 2010;35(1):64-101. PubMed PMID 20052816. DOI: 10.1097/aap.0b013e3181c15c70.” pubmed.ncbi.nlm.nih.gov
- American Society of Regional Anesthesia and Pain Medicine (Horlocker TT, Wedel DJ, Benzon H, et al.). “"Regional anesthesia in the anticoagulated patient: defining the risks (the second ASRA Consensus Conference on Neuraxial Anesthesia and Anticoagulation)." Reg Anesth Pain Med 2003;28(3):172-197. PubMed PMID 12772135. DOI: 10.1053/rapm.2003.50046.” pubmed.ncbi.nlm.nih.gov
- Geller AI, Shehab N, Weidle NJ, et al. (Centers for Disease Control and Prevention and U.S. Food and Drug Administration). “"Emergency Department Visits for Adverse Events Related to Dietary Supplements." New England Journal of Medicine 2015;373(16):1531-1540. PubMed PMID 26465986. DOI: 10.1056/NEJMsa1504267.” pubmed.ncbi.nlm.nih.gov
- Cheng B, Hung CT, Chiu W (Hong Kong Medical Journal). “"Herbal medicine and anaesthesia." HKMJ 2002;8(2):123-130..” hkmj.org
- National Institutes of Health, Office of Dietary Supplements. “Dietary Supplements: What You Need to Know (Consumer Fact Sheet).” ods.od.nih.gov