For most people who have had an ischemic stroke, aspirin is a lifelong medication. There is no standard stopping point. The goal shifts over time, from preventing a second stroke in the critical first weeks to reducing long-term cardiovascular risk for years afterward, but aspirin itself typically continues indefinitely unless a doctor has a specific reason to stop or switch it.
That said, the first few months after a stroke involve a more intensive treatment phase that does have a defined timeline. Understanding both phases helps make sense of what your doctor has prescribed and why.
The First 21 to 90 Days: A More Aggressive Phase
The highest risk of a second stroke comes in the days and weeks immediately after the first one. To counter this, many patients are started on two blood-thinning medications together, typically aspirin plus clopidogrel. This combination is called dual antiplatelet therapy, or DAPT.
For minor strokes and transient ischemic attacks (TIAs), the evidence points to a 21-day course of DAPT as the sweet spot. Research combining data from two major clinical trials found that the benefit of using two medications together is strongest in the first 10 days and levels off after that. A 21-day course reduces the risk of another stroke without increasing the risk of serious bleeding. Extending DAPT beyond 21 days, up to 90 days, is sometimes considered for higher-risk patients, such as those with severe narrowing of blood vessels inside the brain or those who experience a second stroke or TIA shortly after the first. But for most people, continuing both medications long-term offers no additional protection over switching to a single agent.
After this short-term dual phase ends, the standard approach is to continue on one antiplatelet medication alone.
Long-Term Prevention: Aspirin Continues Indefinitely
Once the acute phase is over, you’ll typically stay on aspirin (or an alternative like clopidogrel) for the foreseeable future. The American Heart Association gives its highest-level recommendation for using an antiplatelet agent in long-term secondary stroke prevention, without specifying a time limit. Aspirin remains the most commonly used option.
The reason is straightforward. Aspirin permanently disables the clotting ability of each platelet it encounters by blocking the production of a chemical that triggers clot formation. Since your body constantly produces new platelets, the effect only lasts as long as you keep taking the drug. Stopping it means new platelets can clot normally again, and your risk of forming a dangerous clot climbs back up.
“Indefinitely” can feel like a vague answer when you’re looking for a number, but in practice it means: unless something changes, like a serious side effect, a new diagnosis, or an upcoming surgery, you stay on it.
Dosage: Low-Dose Works as Well as High-Dose
Most people are prescribed a low daily dose, commonly 81 mg. A large randomized trial (ADAPTABLE) directly compared 81 mg to 325 mg daily in patients with cardiovascular disease and found no significant difference in effectiveness or safety between the two doses. This held true for both men and women. The lower dose has become the default for long-term use because it offers the same protection with potentially less stomach irritation.
How Aspirin Compares to Clopidogrel
Your doctor may prescribe clopidogrel instead of aspirin for long-term prevention, especially if you can’t tolerate aspirin. Both are considered acceptable options in current guidelines. However, the evidence for which is better specifically in stroke patients is more nuanced than many people realize.
The most well-known head-to-head trial, CAPRIE, found clopidogrel slightly better overall across all types of vascular disease, but when researchers looked only at the subgroup of stroke patients, clopidogrel was not more effective than aspirin. A large retrospective study of first-time ischemic stroke patients actually found that those on aspirin had lower rates of major cardiovascular events at one year. The clopidogrel group had a 1.78-fold higher risk of these events compared to the aspirin group, including higher rates of recurrent stroke and heart attack. The risk of death was similar between the two.
This doesn’t mean clopidogrel is a bad choice. Individual factors like medication tolerance, other health conditions, and genetic differences in how your body processes these drugs all play a role. But aspirin remains a strong first-line option.
Bleeding Risk Over Time
The main trade-off with long-term aspirin use is bleeding, particularly in the digestive tract. A meta-analysis of long-term aspirin trials found that gastrointestinal bleeding occurred in about 2.5% of aspirin users compared to 1.4% on placebo over an average of 28 months. Even at doses below 163 mg per day, the risk was still elevated at 2.3% versus 1.45%. Expressed another way, for every 248 people taking low-dose aspirin for one year, one will experience a gastrointestinal bleed that wouldn’t have happened without the drug.
For someone whose baseline risk of a second stroke is far higher than this bleeding risk, the math strongly favors continuing aspirin. But the calculation can shift for older adults, people with a history of stomach ulcers, or those on other blood-thinning medications. This is typically why doctors periodically reassess whether aspirin is still the right choice rather than simply prescribing it and forgetting about it.
After a Hemorrhagic Stroke
Everything above applies to ischemic strokes, which are caused by blood clots. If your stroke was caused by bleeding in the brain (a hemorrhagic stroke), the situation is more complicated. Taking a drug that reduces clotting after a bleed-type stroke sounds counterintuitive, and the decision involves weighing competing risks.
The RESTART trial, published in The Lancet, examined whether restarting antiplatelet therapy after a brain bleed was safe. The findings suggested that the risk of another brain bleed from restarting antiplatelet therapy was low, while ischemic strokes and heart attacks were two to three times more common than recurrent hemorrhages. Among patients in the trial, the median time between the hemorrhagic stroke and restarting antiplatelet therapy was 76 days, though the optimal timing remains uncertain. Roughly a third of patients with a history of brain hemorrhage are now restarted on antiplatelet therapy, but this is a highly individualized decision that depends on why you were on aspirin in the first place and the specific characteristics of your bleed.
When Aspirin Gets Paused
The most common reason for temporarily stopping aspirin is an upcoming surgery. Aspirin’s clot-blocking effect lasts for the entire 7-to-10-day lifespan of the platelets it has already affected, so surgeons often ask patients to stop it about a week before a procedure to reduce surgical bleeding. For stroke patients, this pause is kept as short as possible because the risk of a clot-related event doesn’t disappear just because surgery is scheduled. In many lower-risk surgeries, aspirin is continued straight through. The decision depends on the type of procedure and your individual stroke risk.