Vitamins and Supplements Before Surgery: Bleeding, Anesthesia and What Surgeons Ask
Why surgical and anesthesia teams ask about vitamins, which ones come up most (vitamin E, vitamin K, biotin), what sources say about timing, and what to bring to your visit.
Content last updated . This page has not been medically reviewed.
Why surgical teams ask
The ASA's patient brochure (2015) says that even supplements taken without problems can raise the risk of surgery because some of them prolong the effects of anesthesia, increase bleeding risk, raise blood pressure or interfere with other medicines. [2] It says vitamins count, and notes that studies show half of people who use herbal supplements do not tell their doctors before surgery. [2] The brochure also points out that the ingredient levels in each product can vary, and some levels might not be safe. [2]Vitamins that come up most often
| Vitamin | Why it is raised | What the sources say | Evidence label |
|---|---|---|---|
| Vitamin E | Possible bleeding effect | MedlinePlus says high-dose vitamin E supplements (alpha-tocopherol) might increase the risk of bleeding in the brain (hemorrhagic stroke). [3] A 2010 meta-analysis of nine placebo-controlled trials (118,765 people) found haemorrhagic stroke risk was higher with vitamin E (relative risk 1.22, interval 1.00 to 1.48), about one extra case per 1,250 people taking it. [4] The NHS says there is not enough evidence to know the effects of high daily doses. [5] | Mixed; the trials were about stroke, not surgery |
| Vitamin K | Interacts with warfarin | MedlinePlus says sudden changes in vitamin K intake can change how warfarin works, and to ask your provider about monitoring intake. [6] See Vitamins and blood thinners. | Established interaction |
| Biotin (B7) | Can distort lab results | A US FDA safety communication (2017, as reprinted by the ASA) says biotin can significantly interfere with certain lab tests and cause incorrect results that may go undetected, including tests for cardiac markers such as troponin. [7] See Biotin and lab-test interference. | Regulator warning |
| Multivitamins | May contain biotin | The FDA communication says biotin is found in multivitamins, including prenatal ones. [7] | Depends on the label |
Proper evidence not found for vitamin C, vitamin D, thiamin, B6, B12 or folic acid: I searched the NHS vitamin pages, MedlinePlus vitamin pages, NCCIH and the ASA brochure for surgery-specific bleeding or anesthesia guidance on these and found none. That is not proof of safety; it only means these sources did not address it.
What to bring and ask
- A full list of everything you take, with amounts. The ASA suggests bringing the actual medicine and supplement bottles to your appointment. [2]
- Ask whether any should be paused, and for how long. Timing is set by your team; sources differ, and the only figure read for this page is the ASA's "at least two weeks" in some cases. [2]
- Ask what to do about prescribed medicines. Only your team can answer.
- If you have kidney or liver disease, say so, because it changes how vitamins are handled. See Vitamins and kidney or liver disease.
- After weight-loss surgery, vitamin needs change for life. See Vitamins after bariatric surgery.
Quality and labels
Product strength can vary between brands and batches. See Quality testing and certifications and the general guide Supplements before surgery. Interactions with medicines are covered at Medication interactions.Frequently asked questions
Should I stop my vitamins before surgery?
Ask your surgeon and anesthesiologist. The ASA says that in some cases the anesthesiologist may recommend stopping supplements at least two weeks before a procedure. [2] Do not stop prescribed medicines without their advice.
Is vitamin E the one to worry about?
It is the vitamin most often raised for bleeding. MedlinePlus says high doses might increase hemorrhagic stroke risk, and a meta-analysis found a small increase in haemorrhagic stroke in trials. [3][4] Those studies were not about surgery, so tell your team what you take and let them decide.
Do I need to mention a multivitamin?
Yes. The ASA brochure asks patients to include vitamins, and a multivitamin may contain biotin, which can affect some lab tests. [2][7]
Can vitamins affect blood tests before surgery?
Biotin can. The FDA warned that biotin can cause incorrect results on some lab tests, so tell the lab and your clinician if you take it. [7]
Why do so many people not mention supplements?
The ASA brochure says studies show half of herbal supplement users do not tell their doctors before surgery, because many people do not think of it. [2]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read the evidence labels
Labels used on this page: established nutritional role, evidence in adequately nourished people, mixed, insufficient evidence.
Pregnancy, children and older adults
References
- NCCIH (US National Institutes of Health). Using Dietary Supplements Wisely. Last updated January 2019. Read 2026-10-22.
- American Society of Anesthesiologists (US). Herbal and Dietary Supplements and Anesthesia (patient brochure, copyright 2015). Read 2026-10-22.
- MedlinePlus (US National Library of Medicine). Vitamin E. Review date 21 January 2025. Read 2026-10-22.
- Schürks M et al. Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials. BMJ 2010;341:c5702. PubMed abstract. Read 2026-10-22.
- NHS (UK). Vitamins and minerals: Vitamin E. Page last reviewed 3 August 2020. Read 2026-10-22.
- MedlinePlus (US National Library of Medicine). Vitamin K. Review date 21 January 2025. Read 2026-10-22.
- American Society of Anesthesiologists (US). Biotin (Vitamin B7): Safety Communication - May Interfere with Lab Tests (reprint of a US FDA safety communication, 13 December 2017). Read 2026-10-22.