Ibuprofen: what it does and what to watch
Also known as: Ibuprofen BP, Isobutylphenylpropionic acid · NSAID (nonsteroidal anti-inflammatory pain reliever) · Updated 2026-10-25 · Educational — not medical advice
In plain language: It blocks enzymes called COX-1 and COX-2 that produce prostaglandins, the chemical messengers behind pain, swelling, and fever. That's a double-edged sword: the same prostaglandins also protect the stomach lining and help kidneys regulate blood flow, which is why ibuprofen can cause stomach irritation or affect kidney function if used often or in higher amounts.
What it's used for
- Pain relief (headaches, muscle and joint pain, dental pain)
- Reducing inflammation and swelling
- Fever
- Menstrual cramps
Common side effects
- Stomach upset or heartburn
- Nausea
- Headache or dizziness
- Mild fluid retention or ankle swelling
- Drowsiness
Get medical help if…
Black or tarry stools, or vomit that looks like coffee grounds (possible internal bleeding): go to an emergency department now
Reduced urination, swelling, or unusual tiredness (possible kidney strain)
Chest pain, shortness of breath, weakness on one side of the body or slurred speech (possible heart attack or stroke): call emergency services now
Swelling of the face or throat: call emergency services now. A severe skin rash, especially with blisters or peeling: go to an emergency department now
Severe stomach pain that doesn't go away
Lab values it can move
Few guides tell you this part: medicines show up in blood work. If you take Ibuprofen and a value below looks off on your report, this may be part of the story — never stop a medicine without your doctor.
Ibuprofen can reduce blood flow through the kidneys, so a rising creatinine can signal the kidneys are working harder than usual, especially with frequent use, dehydration, or existing kidney concerns.
CreatinineBecause ibuprofen can irritate the stomach lining enough to cause slow, hidden blood loss, a falling hemoglobin over time is sometimes the first clue of that GI irritation.
HemoglobinGood to know
- Not for babies under 3 months or under 5 kg; avoid in chickenpox or dehydration, and in children with asthma unless a doctor advises it
- Taking it with food or milk reduces stomach irritation
- Avoid combining with other NSAIDs, and check with a doctor before combining with blood thinners or steroids
- People with kidney disease, heart failure, or high blood pressure are usually advised to use it cautiously and only short-term
- Generally avoided during pregnancy unless a doctor or pharmacist advises it, and especially from about 20 weeks; paracetamol is usually preferred
- Limiting alcohol reduces the added risk of stomach irritation
Questions people ask
Why does ibuprofen upset some people's stomachs?
The same prostaglandins ibuprofen blocks to relieve pain and swelling also normally help protect the stomach's inner lining by keeping mucus and blood flow steady there. With those protective prostaglandins reduced, stomach acid can irritate the lining more easily, which is why it's usually recommended to take ibuprofen with food and why long-term daily use is watched more carefully.
Can ibuprofen affect the kidneys even in a healthy person?
Yes, though it's usually temporary and reversible. Ibuprofen narrows some of the blood vessels supplying the kidneys, which matters more when someone is dehydrated, has existing kidney or heart conditions, or takes it frequently over a long period. Doctors often check kidney function tests like creatinine if ibuprofen is needed regularly rather than occasionally.
Is ibuprofen or paracetamol better for inflammation?
Ibuprofen generally has an advantage for pain that comes with visible swelling or inflammation, such as a sprained joint, because it directly blocks the inflammatory chemicals involved. Paracetamol mainly dampens pain and fever signals in the brain without much anti-inflammatory action. The right choice often depends on other health conditions, which is worth discussing with a doctor or pharmacist.
Sources
Taking Ibuprofen? See what your blood work says.
Upload your lab report — every value checked and explained. Free — no account needed.