What organ does aspirin damage? The effects of aspirin on your body

October 12, 2025 •

5 min read

While aspirin is a common over-the-counter pain reliever and blood thinner, its systemic and local effects can harm several vital organs. A major concern for long-term or high-dose use is the damage it can inflict, particularly the question: What organ does aspirin damage? This article will explore the specific organs at risk and the mechanisms behind aspirin's adverse effects.

Quick Summary

Aspirin can harm multiple organs, primarily the stomach, kidneys, and liver. It irritates the stomach lining, inhibits protective prostaglandins, and can cause ulcers and bleeding. High doses or long-term use can negatively affect kidney function and may cause reversible liver injury (hepatotoxicity), especially at high doses.

Key Points

Gastrointestinal Tract: Aspirin most commonly damages the stomach lining by reducing protective prostaglandins, which can lead to erosions, ulcers, and bleeding.
Kidneys: High doses and long-term use can harm the kidneys by reducing blood flow, potentially causing acute kidney injury or fluid retention, particularly in those with existing kidney problems.
Liver: High, long-term aspirin doses can cause reversible liver injury (hepatotoxicity), while use in children with a viral illness carries a risk of Reye's syndrome, a serious condition affecting the liver and brain.
Brain: Aspirin's antiplatelet effects, while beneficial for preventing clots, increase the risk of hemorrhagic stroke (brain bleeding).
Risk Factors: Advanced age, a history of ulcers, and concurrent use of other NSAIDs or blood thinners significantly increase the risk of aspirin's side effects.
Dose Dependence: The risk of organ damage, particularly to the kidneys and liver, is more significant with higher aspirin dosages.

Aspirin, or acetylsalicylic acid, is a nonsteroidal anti-inflammatory drug (NSAID) with a long history of use for pain relief, fever reduction, and anti-clotting effects. Its ability to inhibit cyclooxygenase (COX) enzymes is key to both its benefits and its potential for harm. While most people tolerate occasional use well, regular or high-dose aspirin can pose significant risks to several organs, with the stomach being the most commonly affected.

The Stomach and Gastrointestinal Tract: The Most Common Target

Aspirin's adverse effects on the stomach and the rest of the gastrointestinal (GI) tract are the most widely recognized and frequent complications. The damage occurs through a dual mechanism, involving both a direct topical effect and a systemic action.

How Aspirin Damages the Stomach

Topical irritation: Aspirin is acidic, and when trapped within the stomach lining cells, it can directly damage them and increase their permeability.
Prostaglandin inhibition: The systemic effect is arguably more significant. Prostaglandins are hormone-like substances that play a vital role in protecting the stomach lining by promoting the secretion of mucus and bicarbonate and maintaining mucosal blood flow. By inhibiting the COX-1 enzyme, aspirin reduces the production of these protective prostaglandins, leaving the stomach's delicate lining vulnerable to stomach acid and pepsin.
Antiplatelet effects: As a blood thinner, aspirin inhibits platelet aggregation. If mucosal injury or a stomach ulcer forms, this antiplatelet effect can exacerbate bleeding, potentially leading to a gastrointestinal hemorrhage.

The Spectrum of Gastrointestinal Damage

Aspirin's effect on the GI tract can range from mild indigestion to serious, life-threatening complications. The risk increases with dosage and duration of use, though even low-dose aspirin can cause problems.

Dyspepsia and heartburn: These are common and often the first symptoms of stomach irritation.
Erosions and ulcers: A weakening of the stomach lining can lead to erosions or deeper, more serious peptic ulcers. Worryingly, many individuals with ulcers may be asymptomatic, presenting only when a more severe complication like bleeding occurs.
Gastrointestinal bleeding: Both upper and lower GI bleeding can occur. Symptoms include black, tarry stools; vomiting blood; or feeling dizzy and faint.

Aspirin's Impact on the Kidneys

Like other NSAIDs, aspirin can affect the kidneys, particularly with high doses or long-term use.

The Role of Prostaglandins in Kidney Function

In the kidneys, prostaglandins help regulate blood flow, especially when a person is dehydrated or has pre-existing kidney, liver, or heart disease. Aspirin's inhibition of prostaglandins can decrease the blood flow to the kidneys, leading to several potential complications.

Potential Kidney Complications

Acute Kidney Injury (AKI): The reduction in renal blood flow can trigger a sudden decline in kidney function, especially in individuals with compromised renal health. This effect is reversible upon stopping the medication.
Fluid retention: The inhibition of prostaglandins can also lead to sodium and water retention, causing swelling.
Analgesic nephropathy: Long-term, heavy use of combination analgesic products (historically containing phenacetin with aspirin and other agents) was linked to this chronic kidney disease. While the risk with modern aspirin use is much lower, especially with low doses, care is still warranted, particularly in older adults.

The Liver: The Risk of Hepatotoxicity

While acetaminophen is more famously linked to liver damage, aspirin can also cause liver injury (hepatotoxicity), especially in high doses.

Mechanisms of Liver Damage

Hepatotoxicity: High, long-term aspirin doses can cause elevations in liver enzymes, which typically resolve once the medication is stopped. Cases of severe liver injury in adults are rare but have been reported.
Reye's syndrome: A rare but dangerous condition, Reye's syndrome involves liver and brain damage and is strongly associated with giving aspirin to children and teenagers recovering from a viral illness like the flu or chickenpox. This risk is why aspirin is not recommended for pediatric use unless specifically prescribed by a doctor.

The Brain: The Risk of Hemorrhagic Stroke

One of aspirin's primary functions is to prevent blood clots. However, this antiplatelet effect carries an inherent risk of bleeding elsewhere in the body, including the brain.

Hemorrhagic Stroke

For some individuals, especially those with an increased risk of bleeding, daily aspirin use can raise the risk of a hemorrhagic stroke, where a blood vessel in the brain ruptures. The benefit-risk balance of daily aspirin for heart attack or stroke prevention must be carefully weighed with a healthcare provider, especially considering the elevated bleeding risk in older adults.

Risk Factors for Aspirin-Induced Organ Damage

Several factors can increase an individual's susceptibility to aspirin's adverse effects:

Advanced Age: The risk of both GI bleeding and kidney issues increases significantly with age.
History of GI Ulcers or Bleeding: Previous gastrointestinal problems dramatically raise the risk of recurrence with aspirin use.
Concurrent Medication Use: Taking aspirin with other NSAIDs (like ibuprofen), anticoagulants (like warfarin), or corticosteroids increases the risk of bleeding and ulceration.
Pre-existing Conditions: Liver, kidney, or heart disease can increase the risk of complications.
Alcohol Consumption: Drinking three or more alcoholic beverages daily while taking aspirin increases the risk of stomach bleeding.
H. pylori Infection: This bacteria is a major cause of peptic ulcers and can act synergistically with aspirin to cause greater damage.

Aspirin vs. Other Common Pain Relievers


Feature	Aspirin	Acetaminophen (e.g., Tylenol)	NSAIDs (e.g., Ibuprofen, Naproxen)
Primary Organ Risk	Stomach (bleeding/ulcers)	Liver (overdose)	Stomach, Kidneys (high doses)
Mechanism of Action	Irreversible COX inhibition	Primarily central pain relief	Reversible COX inhibition
Effect on Platelets	Strong anti-clotting effect	Minimal	Moderate anti-clotting effect
Gastrointestinal Risk	High, especially long-term or high dose	Low	High, similar to aspirin
Kidney Risk	Yes, especially high dose/existing disease	Possible, especially in overdose	Yes, especially high dose/existing disease
Reye's Syndrome	High risk in children/teens with viral illness	No risk	No risk

Conclusion: A Balanced Perspective

While aspirin is a valuable medication, it is not without risks. The answer to what organ does aspirin damage? is multi-faceted, with the stomach, kidneys, liver, and brain all being potential sites of adverse effects. The severity of the damage is often dose and duration-dependent and is heavily influenced by individual risk factors. For low-dose daily aspirin users, the most prominent risk is gastrointestinal bleeding. For high-dose or long-term users, particularly those with pre-existing conditions, the risk of kidney or liver damage increases. Ultimately, a discussion with a healthcare provider is essential to weigh the benefits of aspirin against the potential risks for any individual, especially before starting a regular regimen.

For more detailed information on drug-induced liver injury, consult the LiverTox database from the National Institutes of Health.

Frequently Asked Questions

The primary organ that aspirin can damage is the stomach and gastrointestinal tract. This can lead to gastritis, erosions, ulcers, and gastrointestinal bleeding due to the inhibition of protective prostaglandins and direct irritation of the stomach lining.

Yes, even low-dose aspirin can cause gastrointestinal damage, including ulcers and bleeding, although the risk increases with higher doses. The risk of kidney and liver damage is lower with low-dose aspirin in people with normal organ function, but it is not eliminated.

Aspirin affects the kidneys by inhibiting prostaglandins, which are important for maintaining adequate blood flow to the kidneys. In individuals with pre-existing conditions like heart or kidney disease, this can cause a reduction in kidney blood flow and lead to acute kidney injury.

Yes, especially in high doses, aspirin can cause liver injury (hepatotoxicity), though this is often mild and resolves once the medication is discontinued. In children, aspirin is linked to the serious condition Reye's syndrome, which affects both the liver and brain.

No, enteric-coated aspirin is not proven to be safer for preventing gastrointestinal bleeding. While the coating helps it pass through the stomach before dissolving, the systemic effect of inhibiting prostaglandins still increases the risk of bleeding throughout the digestive tract.

Individuals at the highest risk include the elderly, those with a history of stomach ulcers or bleeding, people taking other blood thinners or NSAIDs, and those with pre-existing kidney, liver, or heart disease.

Warning signs include persistent stomach pain, black or tarry stools, vomiting blood, and feeling faint or unusually tired. Any of these symptoms should prompt immediate medical attention.