Which supplements should I stop taking before surgery, and how far in advance?
⚠️ Contact your surgeon or seek care if you experience unusual bruising or bleeding
If you notice unexpected bruising, prolonged bleeding from small cuts, blood in your urine or stool, or feel faint in the days around your surgery, contact your surgical team right away or go to the emergency room. These could be signs of a bleeding or coagulation problem.
Short answer
Many common supplements can increase bleeding risk, interact with anesthesia, or affect your heart and blood pressure during surgery. Most guidelines recommend stopping all herbal and dietary supplements 1 to 3 weeks before any elective procedure. Always tell your surgeon and anesthesiologist exactly what you take, including vitamins and herbal products, since many patients forget to mention these.
What the research shows
A large number of everyday supplements can cause serious problems during and after surgery. The American Society of Anesthesiologists recommends stopping all herbal medications 1 to 3 weeks before elective surgery [3][4]. A consensus panel reviewing 83 different supplements agreed that temporarily stopping them before surgery is the safest default approach [1].
The biggest concerns fall into a few categories:
- Increased bleeding risk: Garlic and hawthorn have the strongest evidence for causing surgical bleeding on their own [8]. Other supplements loosely linked to bleeding include cordyceps, echinacea, and aloe vera [8]. Ginkgo biloba, turmeric, chamomile, fenugreek, milk thistle, melatonin, and bilberry raise bleeding risk if you are also on blood thinners [8]. Evidence on St. John's wort, ginger, and cranberry is mixed [8].
- Anesthesia interactions: Herbs like ginseng, ginkgo, St. John's wort, and echinacea are among the most commonly used supplements that can interfere with anesthetic drugs, causing problems such as irregular heart rhythm, low or high blood pressure, excessive sedation, or liver stress [3].
- Fish oil is a nuanced exception: Although fish oil reduces platelet activity in lab tests, a systematic review of 52 studies found no actual increase in surgical bleeding or transfusions in patients who took it [6]. Still, discuss it with your care team, as many surgeons still prefer you to stop it beforehand.
Why patients often don't realize this matters
Studies show that 50 to 70 percent of surgical patients never mention their supplement use to their doctors, and many do not stop taking them before surgery [3]. In one survey of over 1,400 presurgical patients, only about 17 percent had discontinued herbal remedies before their procedure [2]. Because supplements are sold over the counter and feel "natural," people often don't think of them as medications. But they can affect coagulation, blood pressure, heart rhythm, and how your body processes anesthesia drugs [3][5].
What to ask your surgeon
At your preoperative appointment, bring a complete list (or the actual containers) of every supplement, herb, vitamin, protein powder, or cannabinoid product you take [1][4]. Ask specifically: "Which of these should I stop, and exactly how many days before surgery?" The preoperative clinic visit, usually scheduled at least 2 weeks out, is the ideal time to sort this out [1]. Do not stop any prescription medications on your own without talking to your doctor first.
Caveats
The evidence quality on individual supplements varies widely. Garlic and hawthorn have stronger data supporting a bleeding risk, while the risk from many other herbs is based on smaller or less rigorous studies [8]. For fish oil specifically, the best available evidence does not show a meaningful increase in surgical bleeding [6], though individual surgeons may still ask you to stop it. Guidelines from major anesthesiology societies are based on a precautionary principle: when in doubt, a brief temporary stop is low-risk and potentially protective [1][4].