How Pain Relief Medications Affect Liver and Kidney Health

Most of us rely on painkillers without much thought: aspirin for a headache; ibuprofen for knee pain, muscle pain, toothaches, or arthritis; or paracetamol for a fever. These medicines are genuinely useful, provide effective relief, are easily available, and are generally safe when used correctly. But if used too often, in too high a dose, or with certain ongoing health conditions, these pain medications can affect the functioning of the liver and kidneys.

How Pain Relief Medicines Work

Pain medicines, or analgesics, work in different ways depending on the type. Understanding these differences helps explain why their risks to the vital organs, such as the liver and kidneys, also differ.

• Paracetamol or acetaminophen is a non-opioid analgesic and antipyretic, meaning it relieves mild to moderate pain and reduces fever. It works primarily in the central nervous system by raising the pain threshold. It has a limited anti-inflammatory effect, which is why it does not help much with swollen joints or inflammation [1].
• Ibuprofen and aspirin are NSAIDs (non-steroidal anti-inflammatory drugs) that work by blocking chemicals in the body called prostaglandins, which trigger pain, inflammation, and fever. This makes them particularly effective for conditions involving swelling, such as muscle injuries, arthritis, and dental pain. However, prostaglandins also play a role in maintaining blood flow to the kidneys, which is why NSAIDs can affect kidney function [2].

How Pain Relief Medicines Affect the Liver

1. NSAIDs (Ibuprofen and Aspirin)

NSAIDs are less commonly associated with liver damage than paracetamol. Ibuprofen used at high doses over prolonged periods can rarely cause liver injury, particularly with prolonged high-dose use, and aspirin taken in large amounts has also been linked to liver injury [3]. For most people taking NSAIDs occasionally and at standard doses, the liver risk is low.
A more significant concern with NSAIDs and the liver arises in people who already have liver disease. Advanced liver disease, such as cirrhosis, affects how the blood circulates through the liver and how drugs are processed. NSAIDs can also affect blood clotting by prolonging the time it takes for blood to coagulate, which is a particular concern during procedures such as a liver biopsy or surgery [3].

2. Paracetamol

The liver processes paracetamol. At prescribed doses, the liver metabolises it to non-toxic substances, which are then eliminated from the body via urination. The difficulty arises when excessive amounts of paracetamol are taken at one time or used too frequently over time. When the liver receives more paracetamol than it can process through its normal pathway, it uses an alternative route that produces a toxic byproduct called N-acetyl-p-benzoquinone imine (NAPQI) [4]. At high enough concentrations, NAPQI can damage liver cells and, in severe cases, cause acute liver failure.
Taking paracetamol with alcohol significantly increases this risk. Alcohol depletes the liver’s reserves of the compound (glutathione) that normally neutralises NAPQI. People who drink regularly, have existing liver disease such as hepatitis or cirrhosis, or have severely reduced kidney function should speak to a doctor before taking paracetamol [3].
It is also worth noting that paracetamol is a component of many combination medicines including cold and flu tablets, multi-symptom relief formulas, and some prescription pain medicines. Taking more than one medicine containing paracetamol at the same time can lead to accidental overdose without the person realising it [4].

How These Medicines Affect the Kidneys

1. NSAIDs

NSAIDs are more likely to affect kidney function, while paracetamol primarily affects the liver at high doses. Prostaglandins are the local hormones in the kidneys that help to regulate blood flow into the kidneys, regulate water and sodium balance, and stimulate renin release. NSAIDs suppress prostaglandins. In healthy people with normal kidney function and adequate hydration, occasional NSAID use does not cause significant problems. But in situations where blood flow to the kidneys is already reduced, suppressing prostaglandins can cause the blood vessels leading to the kidneys to narrow, reducing filtration and potentially causing acute kidney injury (AKI) [2].
This risk is higher in people who are dehydrated; elderly; have high blood pressure, heart disease, or existing kidney disease; or who are taking other medicines that affect kidney function, such as diuretics [2]. The National Kidney Foundation advises that people with any stage of kidney disease speak to their doctor before taking NSAIDs, even over-the-counter versions.
Prolonged overuse of NSAIDs at high doses can lead to a gradual and permanent loss of kidney function, known as analgesic nephropathy [2].

2. Paracetamol

Paracetamol, when taken at recommended doses, is generally considered safer for the kidneys than NSAIDs. The National Kidney Foundation notes that paracetamol is often the preferred choice for occasional pain relief in patients with known kidney disease [2]. However, this does not mean it is entirely without risk. At high doses or with long-term use, it can contribute to kidney damage. People with kidney disease should still consult a doctor before using it regularly.

Using Pain Relief Medicines Safely

The following precautions apply to all common pain medicines:

• Use the lowest effective dose for the shortest necessary time. Pain medications are formulated for short-term use in most cases.
• Read every label before taking any product. Many over-the-counter medicines contain paracetamol or an NSAID as one of several ingredients. Check before combining products.
• Dehydration reduces kidney blood flow and heightens NSAID-related kidney risk. So stay well hydrated when taking NSAIDs [2].
• Do not mix NSAIDs with alcohol. This increases the risk of stomach bleeding, and alcohol also compounds the liver risks associated with paracetamol.
• Tell your doctor about every other medication you take. This includes over-the-counter pain medicines, multivitamins, and herbal preparations, all of which may interact with prescription medicines or compound organ risk [2].
• People with liver disease, kidney disease, high blood pressure, or heart disease or those who are pregnant, should not take any pain medicine, including over-the-counter options, without first consulting a doctor.

Who Should Avoid These Medicines

• People with liver disease (especially for paracetamol)
• People with kidney disease (especially for NSAIDs)
• Older adults
• Those taking diuretics, blood pressure meds, or blood thinners
• Pregnant individuals (especially NSAIDs in later pregnancy)

Drug Interactions to Be Aware Of

• NSAIDs + blood thinners

NSAIDs such as ibuprofen, when taken alongside anticoagulants such as warfarin, raise the risk of internal bleeding, including gastrointestinal bleeds. Blood-thinning medication should not be taken with NSAIDs without first consulting the doctor [5].

• NSAIDs + ACE inhibitors/diuretics

The concurrent use of NSAIDs, ACE inhibitors (a type of blood pressure medicine), and diuretics (water tablets) is referred to as the “triple whammy.” Each of these medicines affects kidney blood flow and filtration, and when taken together, their combined effect on the kidneys can be significant enough to trigger acute kidney injury, even in patients with normal kidney function [6].

• Paracetamol + alcohol

When taken in combination with paracetamol, alcohol reduces the liver’s ability to detoxify the toxic product of paracetamol metabolism known as N-acetyl-p-benzoquinone imine (NAPQI). Alcohol does this by lowering levels of glutathione, which is the substance that the liver uses to metabolise NAPQI safely. As a result, even a normal therapeutic dose of paracetamol may lead to liver harm in heavy drinkers [7]. People who consume alcohol regularly are advised to consult a doctor before using paracetamol, even for occasional pain relief.

Warning Signs: When to Speak to a Doctor

Pain medicines can affect the liver and kidneys gradually, often without noticeable early symptoms. Recognising the warning signs early gives your doctor the opportunity to investigate before any damage becomes permanent. If you notice any of the following, particularly after taking pain medicines regularly, seek medical advice promptly.

Signs That May Indicate Liver Stress

• Yellowing of the skin or whites of the eyes (jaundice)
• Persistent nausea, vomiting, or loss of appetite without a clear cause
• Pain or tenderness in the upper right side of the abdomen
• Unusual fatigue that does not improve with rest
• Dark-coloured urine or very pale stools

Signs That May Indicate Kidney Stress

• Swelling in the legs, ankles, or feet (fluid retention)
• Changes in urination, significantly less urine than usual, or foamy urine
• Persistent lower back or flank pain not related to a muscle injury
• Unexplained fatigue, difficulty concentrating, or feeling generally unwell
• High blood pressure that is difficult to control

When NOT to Self-Treat Pain

Do not self-treat if:

• Pain lasts more than a few days
• Pain is severe or worsening
• There is fever with unexplained pain
• You need painkillers daily

Conclusion

Pain medications can be safely used as long as they are used appropriately for the given duration of time. Liver and kidney damage is usually caused by overuse or misuse of pain medication or combining multiple medicines with the same active ingredients without consulting a doctor. Paracetamol, when used within its recommended dosage, is generally the safer choice for people with kidney concerns. NSAIDs may help reduce inflammation, but they do require more consideration, especially if there is pre-existing kidney disease, hypertension or dehydration. Patients requiring ongoing pain management should discuss this issue with their doctor, learn about the effective treatments for pain control, and determine which type of pain reliever would be best suited for the particular situation.

DISCLAIMER: This article is provided for general informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. The information is not a substitute for professional medical consultation. The effects of pain medicines on individual organ health vary depending on age, existing health conditions, other medicines, and dosage. Always consult your doctor before starting, changing, or stopping any medication.

References

[1] National Institute of Diabetes and Digestive and Kidney Diseases. (2016, January 28). Acetaminophen. In LiverTox: Clinical and research information on drug-induced liver injury. National Institutes of Health. https://www.ncbi.nlm.nih.gov/books/NBK548162/

[2] National Kidney Foundation. (2005). Pain medicines and your kidneys: What you need to know. https://www.kidney.org/sites/default/files/pain_medicines.pdf

[3] Hepatitis Victoria / LiverWell. (2020). Painkillers and the liver [Information sheet]. https://www.liverwell.org.au/wp-content/uploads/2020/11/Painkillers-and-the-Liver.pdf

[4] Schaffer, D. H., Murray, B. P., & Khazaeni, B. (2026, March 26). Acetaminophen toxicity. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK441917/

[5] Zheng, Y., Zhang, N., Tse, G., Li, G., Lip, G. Y. H., & Liu, T. (2023). Co-administered oral anticoagulants with nonsteroidal anti-inflammatory drugs and the risk of bleeding: A systematic review and meta-analysis. Thrombosis Research, 232, 15–26. https://doi.org/10.1016/j.thromres.2023.10.011

[6] Calvo, D. M., Saiz, L. C., Leache, L., Celaya, M. C., & Gutiérrez-Valencia, M. (2025). Acute kidney injury and morbi-mortality associated with “triple whammy” combination: Systematic review and meta-analysis. British Journal of Clinical Pharmacology, 91(11), 3031–3041. https://doi.org/10.1002/bcp.70263

[7] Chiew, A. L., & Buckley, N. A. (2023). Paracetamol (acetaminophen) overdose and hepatotoxicity: Mechanism, treatment, prevention measures, and estimates of burden of disease. Expert Opinion on Drug Metabolism & Toxicology, 19(5), 297–317. https://doi.org/10.1080/17425255.2023.2223959

[8] Ahsan, M. U., 1, Ambreen, U., Javed, H., Noor, N., Jan, M., Khan, M. N., D.G. Khan Medical College, CMH Institute of Medical Sciences, People’s University of Medical and Health Sciences for Women, & Department of Medicine, Shaikh Khalifa Bin Zayed Al-Nahyan Medical and Dental College. (2025). NSAID-associated renal injury: Mechanisms, risks, and safer strategies. In Arch Nephrol Ren Stud (Vol. 5, Issue 1, pp. 1–5). https://www.scientificarchives.com/public/assets/articles/article-pdf-1753947157-1492.pdf

[9] Drożdżal, S., Lechowicz, K., Szostak, B., Rosik, J., Kotfis, K., Machoy‐Mokrzyńska, A., Białecka, M., Ciechanowski, K., & Gawrońska‐Szklarz, B. (2021). Kidney damage from nonsteroidal anti‐inflammatory drugs—Myth or truth? Review of selected literature. Pharmacology Research & Perspectives, 9(4), e00817. https://doi.org/10.1002/prp2.817