Diclofenac: what it treats, how to take it, side effects
Last updated September 3, 2026.
Diclofenac is an NSAID - it stops the body's production of the substance that causes pain, fever, and inflammation. It is one of the most prescribed arthritis medicines in the world, and it carries the full NSAID warning label, which deserves a slow read.
What does it treat?
Mild to moderate pain, and the pain, tenderness, swelling, and stiffness of osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis - plus painful menstrual periods, and migraines in adults as a one-dose powder (Cambia) that treats but cannot prevent them. Different forms release differently and cannot be swapped for each other: only take the product your doctor prescribed.
How do you take it?
Depends on the form: capsules three or four times a day on an empty stomach, extended-release tablets once a day, delayed-release tablets two to four times a day, and the migraine powder mixed in 2 to 4 tablespoons of water, drunk immediately. Same times every day if you take it regularly. Missed dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: diarrhea or constipation, gas or bloating, headache, dizziness, and ringing in the ears.
- Serious - stop taking it and call your doctor immediately: stomach pain, heartburn, vomiting blood or material that looks like coffee grounds, blood in the stool, or black tarry stools (the bleeding picture); chest pain, shortness of breath, weakness on one side, or slurred speech (the heart and stroke picture - 911); unexplained weight gain, swelling of the abdomen, feet, or ankles; yellowing skin or eyes, dark or bloody urine; rash, blisters, hives, or facial swelling; and unusual tiredness or pale skin.
Who should not take it?
Anyone who recently had a heart attack, unless their doctor directs it - and never right before or after coronary bypass surgery. The heart attack and stroke risk can arrive without warning and climbs with long use; the stomach ulcer and bleeding risk climbs with age, poor health, long use, and heavy alcohol. Blood thinners like warfarin, aspirin, other NSAIDs, oral steroids, and SSRI or SNRI antidepressants all multiply the bleeding risk - your doctor needs the full list. Flag asthma with nasal polyps, heart failure, swelling, liver or kidney disease, and any past ulcer or bleeding. Around 20 weeks of pregnancy or later it can harm the fetus and complicate delivery. At 75 or older, the risks-and-benefits talk is explicit. The Zipsor capsules contain cow proteins - milk, beef, or gelatin allergy goes on the list - and the migraine powder contains aspartame, which matters with PKU.
When is it an emergency?
Chest pain, one-sided weakness, slurred speech, or trouble breathing is a 911 call - the warning says these events may happen without warning. Vomiting blood or black tarry stools means same-day care. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
Why does diclofenac warn about heart attacks?
Every non-aspirin NSAID carries this warning, and MedlinePlus states it plainly: people taking these drugs may have a higher risk of heart attack or stroke than people who do not - events that may happen without warning and may cause death. The risk climbs with longer use and with existing risk factors like smoking, high blood pressure, high cholesterol, and diabetes. A recent heart attack or upcoming bypass surgery makes it a no unless your doctor directs otherwise.
Why can't I take ibuprofen while on diclofenac?
They are the same class - two NSAIDs at once doubles the stomach ulcer and bleeding risk without doubling the benefit. MedlinePlus names aspirin, ibuprofen, naproxen, and salicylate pain relievers as do-not-start products while taking diclofenac. One NSAID at a time, chosen by your doctor.
Why does my diclofenac say not to switch to another version?
Because the products release the drug differently - capsules, delayed-release tablets, extended-release tablets, and the migraine powder all behave differently in the body, and MedlinePlus says they cannot be used interchangeably. The pharmacy substituting a different diclofenac product without your doctor is not a same-drug swap. Only the prescribed product.
Can I drink alcohol while taking diclofenac?
The warning math says go very light: MedlinePlus lists drinking large amounts of alcohol while taking diclofenac among the factors that raise the risk of ulcers and stomach bleeding - which can happen without warning symptoms. An occasional drink is a doctor conversation; regular heavy drinking on this drug is a real risk.
Why did my doctor ask about my antidepressant before prescribing diclofenac?
SSRIs (like sertraline or fluoxetine) and SNRIs (like duloxetine or venlafaxine) thin the blood's clotting ability, and MedlinePlus lists them among the medications that raise NSAID bleeding risk - alongside warfarin, aspirin, and oral steroids. The combination is often still fine, but it changes the monitoring, which is why the full medication list matters here.
What happens if I miss a dose of diclofenac?
Take it as soon as you remember, unless it is almost time for the next one - then skip it and never double up. The migraine powder is the exception by design: it is a single as-needed dose at the start of a migraine, so there is no schedule to miss.