Aspirin can disrupt sleep, though outright insomnia from a single dose is uncommon. The most well-documented effect is suppression of melatonin, the hormone that signals your brain it’s time to sleep. Aspirin also reduces slow-wave sleep, the deepest and most restorative stage of your sleep cycle. Whether these effects actually keep you awake depends on the dose, when you take it, and what else is in the pill.
How Aspirin Interferes With Sleep Hormones
Aspirin works by blocking the production of chemicals called prostaglandins. That’s what makes it useful for pain and inflammation. But prostaglandins also play a role in melatonin production and body temperature regulation, both of which are essential for normal sleep.
A study published in the journal Physiology & Behavior found that NSAIDs like aspirin suppressed nighttime melatonin levels compared to placebo. Participants who took NSAIDs also experienced a flattening of their normal nighttime body temperature drop. That drop in core temperature is one of your body’s key signals that it’s time to sleep. When it’s blunted, falling asleep becomes harder.
Separately, research on healthy subjects found that 600 mg of aspirin taken three times daily led to a significant reduction in slow-wave sleep. This is the deep sleep your body relies on for physical recovery and memory consolidation. Even if you technically fall asleep, losing slow-wave sleep can leave you feeling unrefreshed the next morning.
The Caffeine Factor in Combination Products
If you’re taking an over-the-counter headache product that contains aspirin, there’s a good chance caffeine is the real culprit behind your sleep trouble. One of the most widely used OTC migraine formulas combines 250 mg of aspirin, 250 mg of acetaminophen, and 65 mg of caffeine per tablet. The recommended dose is two tablets, which delivers 130 mg of caffeine, roughly equivalent to a strong cup of coffee.
Caffeine has a half-life of about five to six hours, meaning half of it is still circulating in your bloodstream hours after you take it. If you take a combination headache product at 6 p.m., you could still have meaningful caffeine levels at midnight. Before blaming aspirin alone, check the label for caffeine.
When Aspirin Might Actually Help Sleep
The relationship between aspirin and sleep isn’t purely negative. If pain or inflammation is what’s keeping you awake, aspirin’s anti-inflammatory effect can improve sleep quality by removing the thing that was disrupting it in the first place.
A 2024 study in Brain, Behavior, and Immunity investigated low-dose aspirin in people undergoing experimental sleep restriction. Participants who took low-dose aspirin showed decreased time spent awake after initially falling asleep and improved sleep efficiency during recovery sleep. The researchers attributed this to aspirin’s ability to dampen the inflammatory response triggered by sleep loss. In other words, when inflammation is part of the problem, aspirin may help rather than hurt.
This creates a practical distinction. If you’re taking aspirin for a headache or joint pain that would otherwise keep you tossing and turning, the net effect on your sleep is likely positive. If you’re taking it preventively (for heart health, for example) and you have no pain keeping you up, the melatonin suppression and slow-wave sleep reduction could work against you.
Timing Your Dose Matters
For people who take daily aspirin for cardiovascular reasons, the timing of your dose may influence both your sleep and the drug’s effectiveness. A meta-analysis of six randomized controlled trials involving over 1,300 patients with cardiovascular disease or hypertension found that bedtime aspirin dosing reduced systolic blood pressure by about 3.65 mmHg and diastolic blood pressure by about 1.92 mmHg compared to morning dosing. Both differences were statistically significant.
This suggests bedtime dosing has cardiovascular advantages. But if you’re someone who notices sleep disruption after taking aspirin, switching to a morning dose is a reasonable tradeoff. The blood pressure benefit of bedtime dosing is modest, and losing sleep consistently carries its own cardiovascular risks.
Salicylate Sensitivity and Sleep
Some people have a heightened reaction to salicylates, the active class of compounds in aspirin. Salicylate intolerance stems from an altered response in how the body processes certain inflammatory pathways. The classic symptoms are respiratory (nasal congestion, sinus polyps, asthma flare-ups), skin reactions like hives, and gut symptoms like diarrhea or abdominal discomfort.
While insomnia isn’t listed as a primary symptom of salicylate intolerance, the secondary effects can easily disrupt sleep. Nasal congestion interferes with breathing at night, and gastrointestinal discomfort makes it hard to stay asleep. If you notice a pattern of congestion, stomach upset, or skin irritation alongside poor sleep after taking aspirin, salicylate sensitivity is worth considering.
Practical Steps if Aspirin Is Affecting Your Sleep
If you suspect aspirin is interfering with your sleep, a few adjustments can help you narrow down the cause:
- Check for caffeine. Switch from a combination headache product to plain aspirin and see if the problem resolves.
- Shift your timing. If you take aspirin in the evening, try moving it to the morning. This gives your melatonin levels a better chance of recovering by bedtime.
- Lower the dose if appropriate. The melatonin-suppressing and slow-wave sleep effects were documented at moderate to high doses. A low daily dose (81 mg) for heart health is less likely to cause noticeable sleep disruption than 600 mg or more for pain relief.
- Track the pattern. Keep a simple log of when you take aspirin and how you sleep that night. Two weeks of data will reveal whether there’s a consistent connection or whether other factors are at play.