The right daily dose of aspirin depends entirely on why you’re taking it. For heart protection, the standard dose is 81 mg per day. For pain relief, adults typically take 300 to 600 mg every four to six hours, up to a maximum of 12 tablets (at 300 mg each) in 24 hours. These are very different uses with different risks, so the distinction matters.
Low-Dose Aspirin for Heart Protection
When doctors refer to “daily aspirin,” they almost always mean a low dose between 75 and 100 mg. In the United States, the most common version is the 81 mg tablet, sometimes still called “baby aspirin.” This small dose is enough to reduce the blood’s clotting ability without delivering the full anti-inflammatory punch of a pain-relief dose.
Who should actually take it, though, has changed significantly in recent years. The U.S. Preventive Services Task Force now recommends against starting daily aspirin for heart disease prevention if you’re 60 or older. The bleeding risks at that age generally outweigh the benefits. For adults aged 40 to 59 with a 10% or greater chance of a cardiovascular event over the next decade, starting low-dose aspirin is a judgment call to make with a doctor, not an automatic recommendation. This applies only to people who have no history of heart disease, stroke, or increased bleeding risk.
If you’ve already had a heart attack, stroke, or stent placement, the calculus is different. Guidelines recommend 75 to 100 mg daily for ongoing protection, and the evidence consistently supports 81 mg as the right target. In this group, the benefit of preventing a second event clearly outweighs the bleeding risk for most people.
Aspirin Doses for Pain and Fever
For short-term pain relief or fever reduction in adults, aspirin is taken at much higher doses than the cardiac version. The standard recommendation from the NHS is one or two 300 mg tablets every four to six hours, with at least four hours between doses. The ceiling is 12 tablets (3,600 mg) in 24 hours, though most people won’t need anywhere near that amount.
This level of use is meant to be temporary. Taking full-strength aspirin for more than a few days raises the risk of stomach irritation, ulcers, and bleeding. If you need pain relief for longer than that, other options are usually safer.
Bleeding Risks With Daily Use
The most significant downside of daily aspirin is gastrointestinal bleeding. A study of healthy elderly individuals found that daily low-dose aspirin increased the risk of serious GI bleeding by 60% over an average follow-up of nearly five years. The risk of serious upper GI bleeding nearly doubled. People who already have risk factors for GI bleeding, such as a history of ulcers, see even higher rates.
This is the core reason the guidelines have shifted away from recommending aspirin broadly for heart prevention. For someone who has never had a heart attack or stroke, the small reduction in cardiovascular risk can be canceled out by the increased chance of a major bleed, particularly after age 60.
Aspirin During Pregnancy
Pregnant individuals at high risk for preeclampsia are sometimes advised to take 81 mg of aspirin daily. The American College of Obstetricians and Gynecologists recommends starting this between 12 and 28 weeks of gestation, ideally before 16 weeks, and continuing until delivery. This is a specific medical use with specific timing, not a general recommendation for all pregnancies.
Why Children Should Not Take Aspirin
Aspirin is contraindicated for children and teenagers, with very few exceptions. It has been linked to Reye’s syndrome, a rare but serious condition that causes swelling in the liver and brain. The risk is highest when aspirin is given during a viral illness like the flu or chickenpox. The only notable exception is children with certain chronic conditions, such as Kawasaki disease, who may need aspirin under close medical supervision.
Timing Aspirin With Ibuprofen
If you take daily low-dose aspirin for your heart and also use ibuprofen for pain, the timing matters. Ibuprofen can block aspirin’s blood-thinning effect if the two are taken too close together. The FDA recommends taking ibuprofen at least 30 minutes after your aspirin dose, or at least 8 hours before it. This ensures aspirin has time to do its job on your platelets without interference.
Aspirin and Colorectal Cancer
There is some evidence that long-term aspirin use may reduce colorectal cancer risk. A Harvard-led study found that taking aspirin for six years or longer was associated with a 19% decreased risk of colorectal cancer and a 15% decreased risk of any gastrointestinal cancer. However, no specific dose has been firmly established for cancer prevention, and the evidence has gaps around exactly how long and how much aspirin is needed. This potential benefit alone isn’t enough to justify starting daily aspirin.
Signs of Too Much Aspirin
Aspirin toxicity is a real danger at high doses. The earliest symptoms are nausea, vomiting, and ringing in the ears (tinnitus). As toxicity worsens, rapid breathing, fast heart rate, agitation, and confusion can develop. Severe cases can cause high fever, seizures, and loss of consciousness. If you suspect an overdose, this is a medical emergency. Even seemingly small volumes of concentrated salicylate products can be dangerous: a single teaspoon of 98% methyl salicylate contains about 7,000 mg of salicylate, equivalent to roughly 90 low-dose aspirin tablets.