Aspirin and Kidney Health: What You Need to Know

Many people reach for aspirin without thinking twice-headache, fever, or even aches from standing all day. But if you have kidney issues or are at risk, that little white pill might be doing more harm than good. Aspirin isn’t just a simple pain reliever. It’s a powerful drug that affects your blood, your stomach, and yes-your kidneys. And most people don’t realize how deeply it can interfere with kidney function, especially when taken regularly or in high doses.

How aspirin affects your kidneys

Your kidneys don’t just filter waste. They also help control blood pressure, balance fluids, and produce hormones that keep your body running smoothly. Aspirin, like other NSAIDs (nonsteroidal anti-inflammatory drugs), works by blocking enzymes called COX-1 and COX-2. These enzymes help make prostaglandins-chemicals that keep blood flowing to your kidneys. When aspirin lowers prostaglandin levels, your kidneys get less blood. That’s fine for a healthy person occasionally. But if you already have reduced kidney function, that drop in blood flow can push your kidneys into crisis mode.

Studies show that regular aspirin use (three or more times a week) is linked to a higher risk of chronic kidney disease, especially in people over 60. One 2023 analysis of over 120,000 adults found that long-term aspirin users had a 20% higher chance of declining kidney function compared to non-users. It’s not a guarantee, but it’s a real risk. And the damage isn’t always obvious. You might not feel anything until your kidneys are already significantly impaired.

Who’s most at risk?

Not everyone who takes aspirin will hurt their kidneys. But some people are far more vulnerable:

• People with existing kidney disease (even mild)
• Those with diabetes or high blood pressure
• Older adults (65+)
• People taking diuretics or ACE inhibitors
• Anyone who’s dehydrated or has low blood volume

Dehydration is a silent danger. If you’re sweating a lot, not drinking enough water, or have had diarrhea, your kidneys are already working harder. Add aspirin on top, and you’re cutting off their blood supply just when they need it most. This can lead to acute kidney injury-even in people who never had kidney problems before.

One case from a Perth hospital in early 2025 involved a 72-year-old man who took two 100mg aspirin daily for heart health and another two for arthritis pain. He didn’t feel sick, but his creatinine levels jumped 40% in two weeks. He’d been drinking less water because he thought he didn’t need much. His kidneys bounced back after stopping aspirin and rehydrating, but it was a close call.

Aspirin for heart protection: is it worth the risk?

Many people take low-dose aspirin (75-100mg daily) to prevent heart attacks or strokes. That’s still recommended for some-especially those with a history of cardiovascular disease. But guidelines have changed. In 2024, the American Heart Association and the Australian Heart Foundation both updated their advice: aspirin is no longer routinely recommended for healthy adults over 70 without prior heart issues.

Why? Because the risk of bleeding and kidney damage outweighs the benefit for most people in that group. If you’re on daily aspirin for heart protection, don’t stop without talking to your doctor. But do ask: Is it still right for me? Are there safer alternatives? Are my kidneys being monitored?

Doctors now recommend checking kidney function (with a simple blood test for creatinine and eGFR) before starting aspirin-and at least once a year if you’re already taking it long-term.

Alternatives to aspirin for pain and inflammation

If you’re taking aspirin for pain, you have options that are gentler on your kidneys:

• Paracetamol (acetaminophen): This is usually the first choice for people with kidney concerns. It doesn’t affect kidney blood flow like aspirin does. But don’t exceed 3,000mg a day-too much can damage your liver.
• Physical therapy and heat/cold therapy: For joint or muscle pain, movement and compression can be more effective long-term than pills.
• Topical NSAIDs: Gels or creams like diclofenac applied to the skin deliver pain relief with much less impact on the kidneys than swallowing a pill.
• Low-dose corticosteroids (under supervision): For inflammatory conditions like arthritis, these can be safer than daily NSAIDs if used short-term and carefully.

Don’t assume that "natural" remedies are safer. Some herbal supplements, like willow bark (which contains salicin, a compound similar to aspirin), can have the same kidney risks. Always check with your pharmacist before trying anything new.

Signs your kidneys might be affected

Kidney damage often happens quietly. But watch for these red flags:

• Swelling in your ankles, feet, or hands
• Frequent urination, especially at night
• Fatigue or trouble concentrating
• Nausea or loss of appetite
• High blood pressure that’s suddenly harder to control

These symptoms can be caused by many things-but if you’re taking aspirin regularly and notice any of them, get your kidney function tested. A simple blood test can show if your kidneys are struggling.

What to do if you’re on aspirin

If you take aspirin daily, here’s what to do right now:

1. Check your last kidney test results. If you haven’t had one in over a year, schedule one.
2. Review your dosage. Are you taking more than prescribed? Are you combining it with other painkillers?
3. Stay hydrated. Drink water regularly, especially if you’re active or in hot weather.
4. Ask your doctor: "Is this still necessary? Are there safer options?"
5. Never stop aspirin suddenly if it’s for heart protection-this can trigger a clot.

Many people keep taking aspirin out of habit, not because it’s still needed. A 2024 study found that 38% of older adults on daily aspirin had no medical reason to continue it. A quick chat with your GP could save your kidneys.

Final thought: Aspirin isn’t harmless

Aspirin saved lives when it was first introduced. But medicine evolves. What was once seen as a miracle cure is now understood as a tool with serious trade-offs. Your kidneys are hardworking organs. They don’t complain until they’re overwhelmed. Don’t assume that because aspirin is available over the counter, it’s safe for daily use-especially if you’re over 60, have diabetes, or already have high blood pressure.

Ask yourself: Why am I taking this? Is it still helping? Could something else work just as well-with less risk? The answer might not be obvious, but asking the question could make all the difference.