Introduction

Many people with glaucoma take nutritional supplements to support eye health. Common examples are fish oil (omega-3 fatty acids), Ginkgo biloba, garlic, curcumin (turmeric), and combinations like Mirtogenol (pine bark extract plus bilberry). These supplements can have blood-thinning effects by interfering with clotting. Taking several at once (stacking) can amplify those effects. In glaucoma patients, too much blood thinning may lead to more optic disc hemorrhages (small bleeds on the optic nerve) and worse outcomes after eye surgery. This article explains how each supplement works on blood clotting, how their effects can add up, and what patients and doctors can do to manage the risk.

Blood-Thinning Supplements and How They Work

Fish oil (Omega-3 fatty acids). Fish oil pills provide omega-3 fats (like EPA and DHA) that change the behavior of platelets. Animal and lab studies show omega-3s can inhibit platelet aggregation (pmc.ncbi.nlm.nih.gov). In other words, they make platelets less “sticky,” similar to low-dose aspirin. Most clinical trials have not found massive bleeding from fish oil alone, but several case reports warn of trouble when it is combined with other blood thinners. For example, high doses of omega-3 in a patient taking warfarin (plus aspirin) were linked to dangerously high INR (clotting times) and even a subdural brain hemorrhage after a minor fall (pmc.ncbi.nlm.nih.gov). Thus, fish oil can add to bleeding risk, especially if you’re on other anticoagulants.

Ginkgo biloba. Ginkgo leaf extract contains compounds (ginkgolides) that block platelet-activating factor (PAF) (pmc.ncbi.nlm.nih.gov). This effect thins the blood in lab and animal models. In one short clinical study, ginkgo did reduce platelet clumping, though routine clotting tests often stay normal. Still, many reports link ginkgo use to serious bleeds when taken with other anticoagulants. Case reports include spontaneous eye hemorrhages (hyphema), brain bleeds, and excess surgical bleeding in people using ginkgo along with aspirin or warfarin (pmc.ncbi.nlm.nih.gov). In fact, large patient databases show a 38% higher risk of major bleeding when people on warfarin also took ginkgo (pmc.ncbi.nlm.nih.gov). Because of this, guides warn against using ginkgo with any blood thinners.

Garlic. Garlic (Allium sativum) contains allicin and related molecules that inhibit platelets in a dose-dependent way (pmc.ncbi.nlm.nih.gov). In practical terms, eating normal amounts of garlic is generally safe, but high-dose garlic supplements (or aged garlic extracts) can measurably reduce platelet function. There are case reports of garlic boosting INR in patients on warfarin and causing bruising or bleeding sometimes (pmc.ncbi.nlm.nih.gov). For example, one case report showed that adding garlic supplements to warfarin unexpectedly raised the clotting time (INR) (pmc.ncbi.nlm.nih.gov). Overall, garlic’s antiplatelet effect is weaker than aspirin’s, but when combined with other agents it can contribute to bleeding.

Curcumin (Turmeric). The turmeric compound curcumin is a natural anti-inflammatory suspected of blood-thinning effects. Laboratory studies show curcumin blocks platelet activation and aggregation by interfering with enzymes like cyclooxygenase and lipoxygenase (pmc.ncbi.nlm.nih.gov). In other words, curcumin stops the formation of clot-promoting molecules (like thromboxane) and reduces calcium signaling in platelets (pmc.ncbi.nlm.nih.gov). While there are few large human trials on bleeding risk, curcumin’s antiplatelet effect is well documented in animals and in vitro. A recent case report also described a 74-year-old man on clopidogrel and apixaban who developed a large spontaneous thigh hematoma soon after starting 1 gram of curcumin per day (www.jclinmedcasereports.com) (though this source is a case report, it highlights the potential for serious bleeding). Taken together, these data suggest curcumin can contribute to bleeding, especially with other blood thinners.

Mirtogenol. Mirtogenol is a supplement made from Pycnogenol (maritime pine bark extract) plus Mirtoselect (bilberry extract). It is often marketed for eye health because it can improve ocular blood flow and lower eye pressure (pmc.ncbi.nlm.nih.gov). By boosting nitric oxide, Mirtogenol relaxes blood vessels and reduces capillary leak (pmc.ncbi.nlm.nih.gov). Importantly, Mirtogenol is not known as a blood thinner. Its ingredients have antioxidant and vascular effects, but there is no evidence it alters platelet function or clotting. Research on Mirtogenol in glaucoma models shows benefit from better blood flow and lower intraocular pressure (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov), with no reports of excess bleeding. In short, Mirtogenol should not affect bleeding risk like the others do.

Combined (“Stacked”) Effects on Bleeding Risk

When you take more than one blood-thinning supplement at the same time, their effects can add up or even amplify each other. Each supplement generally works in a different way to prevent clotting. For example, fish oil makes platelet membranes less clot-promoting, garlic blocks platelet enzymes, ginkgo blocks PAF signaling, and curcumin blocks clotting chemistry. In theory, combining them hits multiple pathways at once. In practice, stacking can behave like adding up their individual effects – sometimes more, sometimes synergistically more.

There are cases that illustrate this risk. One heart surgery case involved a patient on both fish oil and garlic who developed diffuse bleeding despite normal standard tests (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). In that example, stopping all medications except these supplements did not prevent excessive oozing; the surgeons had to give platelet transfusions. Another report recounts a patient who bled badly on aspirin and warfarin after adding high-dose fish oil (pmc.ncbi.nlm.nih.gov). In lab terms, one old study (in healthy volunteers) found that aspirin alone prolonged bleeding time ~34% and fish oil alone ~9%, but together they prolonged bleeding time ~78% (pubmed.ncbi.nlm.nih.gov). (This is a specific study, but generally it shows how two mild blood thinners together gave a much larger effect.)

In summary, taking multiple supplements with antiplatelet effects can greatly increase bleeding risk. In pharmacodynamic terms, these combinations often have additive actions (reducing clotting from different angles), and sometimes they may even have synergistic effects when one supplement enhances the action of another. The bottom line for patients is that “stacking” should be treated like taking an extra dose of aspirin: it can lead to easier bruising, nosebleeds, or eye hemorrhages.

Interactions with Prescription Anticoagulants

Stacking supplements is especially risky if you are also taking prescription blood thinners. Many anticoagulant drugs work in different ways, but adding supplements can multiply the effect. For instance, warfarin dose is often monitored by the INR. Studies have documented patients whose INR jumped dramatically after starting supplements like ginkgo, garlic or fish oil (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). In one review of medical records, people on warfarin plus ginkgo had a 38% higher bleeding hazard than people on warfarin alone (pmc.ncbi.nlm.nih.gov). Another report found that adding fish oil (omega-3) to warfarin (and aspirin) produced dangerously high INR levels, leading to brain bleeding (pmc.ncbi.nlm.nih.gov).

Even with newer anticoagulants (like Factor Xa inhibitors), similar caution applies. Supplements can alter gut enzymes or platelet function, making drug levels unpredictable. For example, a rat study showed curcumin increased the body’s exposure to clopidogrel (a platelet drug) by ~1.6× (www.jclinmedcasereports.com). Although human data are limited, the combined blood-thinning effect is clear. In practice, doctors often advise against combining herbal supplements with prescription anticoagulants without strict monitoring. If you are on warfarin or a DOAC, adding fish oil, ginkgo, garlic, curcumin, or similar supplements could push you into a dangerous bleeding range.

Effects on Glaucoma: Disc Hemorrhages and Surgery

Glaucoma already damages the optic nerve, and disc hemorrhages (tiny bleeding spots on the optic disc) signal worsening disease. Studies have linked disc hemorrhages with faster visual loss. Notably, use of blood thinners can affect disc hemorrhages. One long-term study found that glaucoma patients taking aspirin had more than double the rate of optic disc hemorrhages compared to those not on aspirin (pubmed.ncbi.nlm.nih.gov). This suggests that any agent that thins blood (including supplements) could similarly increase hemorrhage frequency. In that study, disc hemorrhages tended to occur when eye pressure was lower than usual (pubmed.ncbi.nlm.nih.gov), hinting that vascular fragility plays a role.

By contrast, a more recent analysis found that patients on antiplatelet/anticoagulant drugs had a borderline slower glaucoma progression after a disc hemorrhage than those without – a curious finding (pubmed.ncbi.nlm.nih.gov). This is not fully understood, but it might reflect that better overall circulation could offset some damage for some time. In any case, the main concern remains that extra bleeding (clinically evident or microscopic) can potentially harm the optic nerve. In glaucoma surgery (trabeculectomy or shunt procedures), extra bleeding can cloud the surgeon’s view and affect healing. Although a 2022 study of glaucoma surgeries found no clear increase in severe bleeding events just from antiplatelet drugs (pmc.ncbi.nlm.nih.gov), surgeons still proceed carefully. Even minor bleeding can lead to hematomas or scarring of the surgical site.

Because of these risks, preoperative management often includes stopping supplements. Ophthalmic surgeons generally recommend discontinuing any anticoagulant supplements (and medications) at least 1–2 weeks before eye surgery (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). This mirrors standard practice for aspirin or warfarin. For example, a clinical guideline states that natural products with blood-thinning action should be stopped 2–3 weeks prior to elective surgery (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). (“Elective” means planned glaucoma surgery, not emergency.) If surgery cannot wait, doctors must be ready with measures like platelet transfusions.

Patient Safety Checklist

To manage these risks, patients and doctors can use a simple checklist:**

• Tell your doctor everything. On every visit, list all supplements, herbs, vitamins and “natural” products you take, not just prescriptions. Many patients forget to mention them. (One survey found most surgical patients do use herbal supplements, but often don’t report them (pmc.ncbi.nlm.nih.gov).) In particular, mention fish oil, garlic, ginkgo, curcumin, gingko, ginger, and any glaucoma “cocktails” like Mirtogenol. If you are on aspirin, warfarin, clopidogrel or other blood thinners, this is even more important, since harms often come from mixing. In a large Medicare study, the combinations most associated with bleeding were ginkgo, garlic or ginseng taken with aspirin, warfarin, ticlopidine, etc (pmc.ncbi.nlm.nih.gov).

• Review dose and need. Discuss with your doctor why you take each supplement and whether it’s really necessary. For example, if you take fish oil for heart health but you also take a prescription statin or aspirin, your doctor may adjust therapy rather than risk excess thinning. Similarly, if you’re on no blood thinners but have low blood pressure, even normal-dose omega-3 might need reconsideration.

• Hold before surgery. If you are having any eye procedure (even laser iridotomy or cataract surgery), ask your ophthalmologist which supplements to stop and when. As a rule of thumb, stop any known blood-thinning supplements about 2 weeks before planned surgery (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). This includes high-dose omega-3, high-dose garlic, ginkgo, curcumin, and others. (For minor procedures that don’t cut tissue, like certain laser surgeries, your doctor may allow continuing some, but always check first.) Write it down on the checklist and follow the schedule – missing this step can cause unexpected bleeding in the operating room.

• Monitor for bleeding signs. While you take multiple agents, pay attention to any unusual bleeding: easy bruising, bleeding gums, heavy menstrual bleeding, nosebleeds, or excess tearing/blood in one eye (hyphema). Even small gum bleeds or larger bruises could be a warning. If you notice these, tell your doctor right away. Your doctor may get lab tests (like INR if you use warfarin, or platelet function tests) to gauge if your blood is too thin.

• Coordinate care. Make sure all your doctors and pharmacists know about the supplements. For example, if your cardiologist prescribes clopidogrel or does a stent while you’re on supplements, he or she needs to know. A pharmacist or primary doctor can often warn about interactions (e.g., warfarin clinics monitor INR more closely if you start new herbs). Keep an updated medication (and supplement) list and bring it to appointments.

• Adjust if needed. Sometimes the safest choice is to simply stop extra supplements. For example, if you have new surgery coming, don’t start any new blood-thinning herbs until after recovery. After surgery, your doctor can advise if and when to reintroduce them. Even if your eye pressure or glaucoma is still a concern, it’s better to avoid bleeding risks until healing is done.

Conclusion

Dietary supplements like fish oil, ginkgo, garlic, and curcumin can provide health benefits, but they do act like natural blood thinners. Using several together or with prescription anticoagulants can stack those effects and raise the risk of bleeding. In glaucoma patients, this means a higher chance of optic disc hemorrhages and tougher surgery conditions. There is no simple formula for how much each combination raises bleeding risk, but cases show dramatic effects. The safest approach is open communication: always tell your doctor about all supplements, especially before surgery or if you bleed easily. You and your care team can then weigh the benefits and risks of each agent. With caution and planning (pause supplements before procedures, monitor labs, etc.), you can help prevent dangerous bleeds while still managing glaucoma and overall health.

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