Several widely used medication classes can cause or increase the risk of bleeding, from common pain relievers to prescription blood thinners and even some antidepressants. The risk ranges from minor bruising to serious internal hemorrhage, depending on the drug, the dose, and your personal health profile. Understanding which medications carry this risk helps you recognize warning signs early and have informed conversations about your treatment.
Pain Relievers (NSAIDs and Aspirin)
Nonsteroidal anti-inflammatory drugs are among the most common causes of medication-related bleeding, and millions of people take them without thinking twice. This group includes ibuprofen, naproxen, and aspirin. These drugs work by blocking an enzyme called cyclooxygenase, which has two important consequences: they reduce pain and inflammation, but they also interfere with platelets, the blood cells responsible for forming clots at the site of an injury.
Aspirin is particularly potent because it permanently disables the clotting ability of every platelet it touches. Since platelets live about 7 to 10 days, a single dose of aspirin affects clotting for roughly a week. Other NSAIDs like ibuprofen block clotting only temporarily, wearing off as the drug leaves your system. The most common bleeding site with all of these drugs is the gastrointestinal tract. NSAIDs damage the stomach lining by suppressing protective compounds called prostaglandins, which normally keep the mucous barrier intact and promote tissue repair. This creates a double problem: the stomach lining is more vulnerable to erosion while the blood is simultaneously less able to clot.
The U.S. Preventive Services Task Force now recommends against starting daily low-dose aspirin for heart disease prevention in adults 60 and older. The reasoning is straightforward: both cardiovascular risk and bleeding risk climb with age, and for older adults, the bleeding danger from aspirin (gastrointestinal bleeds, intracranial bleeding, hemorrhagic stroke) outweighs the heart benefits. For people already taking daily aspirin, the task force suggests considering stopping around age 75.
Blood Thinners: Anticoagulants
Anticoagulants are prescribed specifically to prevent dangerous blood clots in conditions like atrial fibrillation, deep vein thrombosis, and pulmonary embolism. They work by interfering with clotting proteins in the blood, slowing the chain reaction that forms a clot. The tradeoff is an inherently higher bleeding risk.
Warfarin, the older anticoagulant, requires regular blood monitoring because its effectiveness fluctuates with diet, other medications, and individual metabolism. When levels drift too high, bleeding risk increases sharply. Research has identified that when the blood-thinning measurement (INR) reaches 8.5 or above, the risk of serious bleeding rises significantly.
Newer blood thinners, often called DOACs (direct oral anticoagulants), include rivaroxaban, apixaban, dabigatran, and edoxaban. These cause less major bleeding overall than warfarin, with rates of about 1% to 4% per year compared to warfarin’s higher rates. They also carry a substantially lower risk of bleeding inside the skull. However, some DOACs are associated with more gastrointestinal bleeding than warfarin. In studies of patients with blood clots in the veins, major bleeding occurred in 1.1% per year with DOACs versus 1.8% with warfarin.
One less obvious danger with these newer blood thinners is drug interactions. Certain medications can raise blood levels of DOACs by blocking their elimination from the body. For example, telmisartan, a common blood pressure medication, was associated with nearly a fivefold increase in bleeding risk when taken alongside DOACs in one study.
Antidepressants (SSRIs)
This one surprises many people. Selective serotonin reuptake inhibitors, the most commonly prescribed class of antidepressants, increase the risk of upper gastrointestinal bleeding by about 55%. The mechanism involves platelets: just as SSRIs prevent brain cells from reabsorbing serotonin, they do the same thing to platelets. Platelets normally store serotonin and release it at injury sites to trigger clot formation and constrict blood vessels. When SSRIs deplete that serotonin supply, platelets become less effective at sealing wounds.
The risk becomes much more serious when SSRIs are combined with NSAIDs. Studies have found that taking both together raises the odds of an upper GI bleed by roughly 4 to 11 times compared to taking neither. This is a particularly important interaction because both drug types are extremely common, and people often take over-the-counter ibuprofen or naproxen without considering how it interacts with their antidepressant.
Corticosteroids
Oral corticosteroids like prednisone and dexamethasone increase the risk of gastrointestinal bleeding or perforation by about 40%. The mechanism isn’t fully understood, but corticosteroids likely impair the body’s ability to repair tissue in the gut lining. They can also mask the pain of a developing ulcer, since their anti-inflammatory and pain-relieving properties may hide symptoms until a bleed becomes serious.
In practice, this risk is most significant for hospitalized patients, who tend to be sicker and on higher doses. For people taking corticosteroids as outpatients, the absolute risk is low: roughly 1.8 bleeding events per 1,000 patients on steroids compared to 0.7 per 1,000 on placebo. Hospitalized patients face a much steeper rate of about 38 per 1,000.
Herbal Supplements
Several common supplements affect bleeding risk, though the evidence varies widely by product. Garlic supplements have the strongest evidence for increasing surgical bleeding, with multiple clinical trials showing they decrease platelet clumping. Hawthorn supplements carry a similar level of concern. Both should be stopped before any planned surgery.
Ginkgo biloba presents a more nuanced picture. On its own, clinical trials haven’t consistently shown a bleeding risk. But in patients taking warfarin, a large review of over 800,000 charts found that adding ginkgo biloba significantly increased the risk of major bleeding events. Chondroitin-glucosamine supplements showed a similar pattern of danger specifically when combined with warfarin.
Some supplements commonly assumed to be risky are actually not. Fish oil, ginseng, and saw palmetto have not been associated with increased bleeding in controlled studies, despite scattered case reports. If you’re on blood thinners and take any supplement, the interaction matters more than the supplement alone.
Who Faces the Highest Risk
The same medication can be relatively safe in one person and dangerous in another. Several factors push bleeding risk higher:
- Age over 75: Older adults eliminate drugs more slowly and are more likely to take multiple medications that interact with each other.
- History of GI problems: Having had ulcers, polyps, esophageal varices, or any previous GI bleeding dramatically raises the chance of another bleed. Recent gastrointestinal lesions within the past three months are among the strongest independent predictors.
- Kidney disease: Impaired kidneys clear many drugs more slowly, allowing blood levels to climb. Multiple studies have consistently linked kidney problems with elevated bleeding risk on blood thinners.
- Multiple blood-affecting medications: Taking an anticoagulant alongside an NSAID, or an SSRI with an NSAID, compounds the danger far beyond what either drug would cause alone.
- Recent trauma or surgery: Physical injury within the preceding two weeks was significantly more common in patients who experienced bleeding events on blood thinners.
- Chronic alcohol use and liver disease: Both impair the liver’s production of clotting factors and its ability to metabolize drugs properly.
Warning Signs of Medication-Related Bleeding
Bleeding from medications doesn’t always look like what you’d expect. The obvious signs are nosebleeds, excessive bruising, and cuts that won’t stop bleeding after 10 minutes. But internal bleeding is harder to spot and more dangerous.
Watch for red or dark brown urine, black or tarry stools (a sign of bleeding in the upper GI tract), or blood in vomit or saliva. Severe headaches that come on suddenly can signal bleeding in the brain, particularly for people on anticoagulants. Unexplained dizziness, faintness, or weakness may indicate significant blood loss that isn’t visible externally. Unusually heavy menstrual periods and large bruises that appear without a clear cause are also warning signs. Abdominal pain that’s new or worsening deserves prompt attention, especially if you’re taking any of the medications discussed here.