Supplements to Stop Taking Before Surgery

Short answer: Several widely used supplements, including fish oil, garlic, and ginkgo biloba, can affect platelet function and bleeding time, which matters greatly in a surgical setting. Most surgeons recommend disclosing all supplements at least two weeks before a scheduled procedure so your care team can advise whether to pause them.

Why Supplements Matter Before Surgery

Many people assume that because supplements are sold without a prescription they are automatically safe to take right up to the day of an operation. That assumption can be risky. Some supplements influence how blood clots form, how anesthesia is processed, or how the immune system responds to stress. Because these products are not intended to diagnose, treat, cure, or prevent any disease, and these statements have not been evaluated by the FDA, their effects in a surgical context are often underappreciated by patients and, sometimes, by clinicians who do not ask about them.

The three supplements reviewed below, omega-3 fatty acids, garlic, and ginkgo biloba, are among the most commonly used in the United States and each carries a documented interaction concern related to bleeding. All information on physiological roles, safety, and evidence ratings in this guide is grounded in data from the NIH Office of Dietary Supplements (ODS) and the National Center for Complementary and Integrative Health (NCCIH). Always talk to your surgeon, anesthesiologist, or pharmacist about your personal supplement routine before any procedure.

Omega-3 Fatty Acids (Fish Oil)

What they are

Omega-3 fatty acids include alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). According to the NIH ODS, ALA is an essential fatty acid, meaning the body cannot make it and it must come from food. The Institute of Medicine set an Adequate Intake (AI) of 1.6 g per day of ALA for adult men and 1.1 g per day for adult women ages 19 to 50. No Recommended Dietary Allowance exists for ALA because data were insufficient to establish an Estimated Average Requirement, and no specific intake recommendation has been set for EPA or DHA. No Tolerable Upper Intake Level has been established for any omega-3.

Physiological roles

The NIH ODS notes that omega-3s serve as structural components of the phospholipids in cell membranes, with DHA especially concentrated in the retina, brain, and sperm. They also act as precursors to eicosanoids, signaling molecules involved in cardiovascular, pulmonary, immune, and endocrine function.

The surgical concern

Omega-3 supplements can reduce platelet aggregation and prolong bleeding time. The NIH ODS notes that when combined with anticoagulant or antiplatelet medications such as warfarin, aspirin, or clopidogrel, there is a theoretical increased risk of bleeding. Clinical trials have generally shown that prolonged bleeding time did not exceed normal limits or cause clinically significant bleeding, but the ODS advises periodic monitoring. High doses, roughly 900 mg per day EPA plus 600 mg per day DHA or more for several weeks, may also suppress inflammatory immune responses. The FDA specifies that supplement labels should not recommend a daily intake of EPA and DHA higher than 2 g from supplements.

Evidence quality (per NIH ODS)

• Omega-3s lower elevated serum triglycerides: Moderate
• Omega-3s reduce risk of most cardiovascular events in the general population: Limited
• Omega-3s prevent cognitive decline or Alzheimer disease: Insufficient

Garlic Supplements

What they are

Garlic supplements are derived from Allium sativum and provide organosulfur compounds including allicin. No dietary reference intake has been established for garlic by the IOM, and no Tolerable Upper Intake Level exists.

Physiological roles

According to the NCCIH, garlic compounds have been studied for modest effects on blood lipids, blood pressure, and blood sugar in people who already have elevated levels of those markers. These are physiological associations observed in research, not established therapeutic claims.

The surgical concern

The NCCIH states clearly that garlic supplements may increase the risk of bleeding, which is particularly relevant around surgical procedures. This risk is compounded when garlic is combined with anticoagulants such as warfarin or antiplatelet medicines such as aspirin. The NCCIH advises disclosing garlic supplement use to your surgeon. Garlic has also been reported to reduce blood levels of saquinavir, an HIV protease inhibitor, illustrating that herb-drug interactions can extend beyond bleeding alone. Oral use has been studied safely for up to seven years, but the perioperative window is a specific exception where caution is warranted.

Evidence quality (per NCCIH)

• Garlic reduces total and LDL cholesterol in people with high cholesterol: Moderate
• Garlic reduces blood pressure in people with hypertension: Limited
• Garlic reduces blood sugar in people with diabetes: Limited
• Garlic influences cancer risk or supports immune function: Insufficient

Ginkgo Biloba

What it is

Ginkgo biloba leaf extract is derived from the ginkgo tree and contains flavonoids and terpene lactones. It is widely marketed for memory and cognitive support. No dietary reference intake or Tolerable Upper Intake Level has been established.

Physiological roles

The NCCIH notes that ginkgo is marketed for memory and thinking, but research has not established a benefit for cognition in healthy adults. It has historically been used for circulation-related complaints, though conclusive modern evidence of benefit is lacking.

The surgical concern

Ginkgo may increase the risk of bleeding, particularly in people who also take anticoagulant or antiplatelet drugs such as warfarin. The NCCIH advises consulting a health care provider before combining ginkgo with any medication. Ginkgo leaf extract is considered likely safe for most adults in moderate oral amounts, with studies lasting up to six years, but the bleeding risk makes it a supplement to discuss and potentially pause before surgery. It may also be unsafe during pregnancy due to a possible risk of early labor or excess bleeding at delivery.

Evidence quality (per NCCIH)

• Ginkgo prevents dementia or cognitive decline in older adults: Insufficient
• Ginkgo improves cognitive performance in healthy people: Insufficient
• Ginkgo relieves symptoms of existing dementia: Limited
• Ginkgo helps heart disease, high blood pressure, or tinnitus: Insufficient

What to Do Before Your Procedure

The most important step is straightforward: bring a complete list of every supplement, herb, and over-the-counter product you take to your pre-operative appointment. Do not wait for your provider to ask. Surgeons and anesthesiologists cannot account for interactions they do not know about.

• Disclose all supplements at least two weeks before a scheduled procedure, or as soon as you know surgery is planned.
• Do not stop or adjust any prescription medication without explicit guidance from your prescribing clinician.
• Ask your pharmacist to review your full supplement and medication list for interactions.
• Consult your clinician for personal dosing guidance. The population reference values cited here are not individual recommendations.

Stopping a supplement for a short window around surgery does not mean it is harmful in everyday use. It simply reflects the specific physiological demands of a surgical setting, where bleeding control and anesthetic metabolism are tightly managed. Open communication with your care team is the most effective tool you have.