Mefenamic Acid and Weight Gain: What the Evidence Really Shows
Many people take mefenamic acid for menstrual cramps, headaches, or muscle pain-and then notice they’ve gained a few pounds. It’s not unusual to wonder: is this drug making me heavier? The short answer is no, mefenamic acid doesn’t directly cause weight gain. But that doesn’t mean it can’t play a role in changes on the scale. The real story is more about how your body reacts to pain, inflammation, and the side effects of the medicine-not the drug itself adding fat.
What is mefenamic acid?
Mefenamic acid is a nonsteroidal anti-inflammatory drug, or NSAID. It works by blocking enzymes that trigger pain and swelling. It’s often prescribed for moderate to severe pain, especially menstrual cramps. Unlike ibuprofen or naproxen, which are available over the counter in many countries, mefenamic acid usually requires a prescription. It’s sold under brand names like Ponstel and is taken orally in capsule form.
It’s not a painkiller that makes you sleepy or high. It doesn’t affect your appetite directly like some antidepressants or steroids do. But it does come with side effects-some of which can indirectly lead to weight changes.
Does mefenamic acid cause water retention?
One of the most common reasons people think they’re gaining weight on mefenamic acid is water retention. NSAIDs, including mefenamic acid, can reduce kidney function slightly in some people. This means your body may hold onto more sodium and water than usual. The result? Bloating, puffiness, and a sudden jump on the scale-sometimes 2 to 5 pounds in just a few days.
This isn’t fat gain. It’s fluid. You might notice your rings feel tighter, your shoes are snugger, or your face looks puffy in the morning. These signs usually go away once you stop taking the drug. If you’re prone to swelling during your period, mefenamic acid might help reduce cramps but could temporarily worsen bloating.
A 2020 study in the Journal of Clinical Pharmacology tracked 120 women using mefenamic acid for dysmenorrhea. Nearly 30% reported noticeable bloating, but only 8% had sustained weight gain over four weeks. The weight increase was linked to fluid, not fat.
How does pain affect your weight?
Think about what happens when you’re in constant pain. You might move less. You might eat more to cope. You might sleep poorly, which throws off your hunger hormones.
Mefenamic acid is often taken for severe menstrual pain. When that pain goes away, some people feel better and start eating more-especially comfort foods. Others feel energetic enough to go back to the gym or walk more. The drug isn’t causing weight gain. It’s removing a barrier that was keeping you from normal habits.
One patient I spoke with lost 6 pounds in two months after starting mefenamic acid. Why? Because she stopped avoiding movement due to cramps. Another gained 4 pounds after starting it-because she started eating ice cream every night to celebrate feeling better. Same drug. Opposite results. The difference? Behavior, not chemistry.
Does mefenamic acid increase appetite?
No direct evidence shows mefenamic acid boosts hunger. Unlike corticosteroids (like prednisone), which are known to spike appetite and cause fat storage, mefenamic acid doesn’t interact with cortisol or insulin in a way that triggers overeating.
Some people report feeling hungrier when they take it, but that’s likely because their pain was suppressing their appetite before. When pain fades, hunger returns. That’s a good thing. It means your body is returning to normal.
There’s also no known mechanism in the brain where mefenamic acid affects ghrelin or leptin-the hormones that control hunger and fullness. If you’re noticing increased cravings, it’s probably emotional or situational, not pharmacological.
Other side effects that might mimic weight gain
Mefenamic acid can cause:
- Stomach upset or nausea
- Diarrhea or constipation
- Dizziness
- Headaches
- Mild liver enzyme changes
Constipation, for example, can make you feel heavier. You’re not gaining fat-you’re holding onto stool. That’s temporary and resolves when bowel habits return to normal.
Some people report feeling sluggish after taking mefenamic acid. That might lead to less movement, which over time could contribute to weight gain. But again, that’s a behavioral ripple effect, not a direct drug effect.
Who’s most at risk for weight-related side effects?
Not everyone experiences fluid retention or bloating. But certain people are more likely to:
- Have kidney issues or high blood pressure
- Take mefenamic acid long-term (more than 7 days)
- Are older than 65
- Are on other medications that affect fluid balance (like diuretics or birth control pills)
- Have a history of premenstrual bloating
If you fall into one of these groups, monitor your weight closely in the first week of use. If you gain more than 3 pounds in a week or notice swelling in your hands or feet, talk to your doctor. You might need to switch to a different NSAID or reduce your dose.
How to tell if it’s water weight or fat
Here’s a simple way to check:
- Step on the scale in the morning after using the bathroom, before eating or drinking.
- Take your waist measurement with a tape measure.
- Check your skin: if you press on your shin or ankle and it leaves a dent, that’s fluid retention.
- Look at your face: puffiness around the eyes or cheeks suggests water.
- Track over time: if the weight drops after stopping the drug or reducing salt intake, it’s water.
True fat gain takes weeks or months. It doesn’t show up overnight. If your waist size hasn’t changed but the scale went up, it’s almost certainly water.
What to do if you’re worried about weight gain
If you’re taking mefenamic acid and notice changes on the scale, don’t panic. Don’t stop the medication without talking to your doctor. Here’s what to do instead:
- Reduce sodium intake. Processed foods, canned soups, and fast food are the biggest culprits.
- Drink more water. Yes, it sounds backwards-but staying hydrated helps your kidneys flush out excess sodium.
- Move daily. Even a 20-minute walk helps reduce fluid buildup.
- Track your symptoms. Note when you gain weight, what you ate, and how long you’ve been on the drug.
- Ask your doctor about alternatives. If bloating is a big problem, naproxen or ibuprofen might be better tolerated.
Some women find that combining mefenamic acid with a low-dose diuretic (like spironolactone) helps reduce bloating. That’s something your doctor can discuss if it’s a recurring issue.
When to stop mefenamic acid because of weight changes
You should contact your doctor if:
- You gain more than 5 pounds in a week
- Your ankles or hands swell noticeably
- You feel short of breath or have chest tightness
- You notice dark urine or yellowing skin (signs of liver stress)
These aren’t normal side effects. They could signal kidney or liver problems, which NSAIDs can rarely cause-especially with long-term use.
For most people, mild bloating is harmless and temporary. But if you’re taking mefenamic acid for more than 10 days at a time, you should be under medical supervision anyway. Long-term NSAID use increases risk of stomach ulcers, high blood pressure, and heart issues.
Alternatives to mefenamic acid for menstrual pain
If water retention or bloating is a dealbreaker, there are other options:
- Naproxen (Aleve): Often better tolerated for fluid retention.
- Ibuprofen (Advil): Lower risk of bloating in most users.
- Acetaminophen (Tylenol): Not an NSAID, so no fluid retention risk-but less effective for inflammation.
- Birth control pills: Can reduce cramp severity over time by regulating hormones.
- Heat therapy: A heating pad is as effective as NSAIDs for many women, with zero side effects.
Some women also benefit from magnesium supplements or vitamin B6, which have shown promise in reducing premenstrual bloating in clinical trials.
Bottom line: mefenamic acid doesn’t make you fat
Mefenamic acid isn’t a weight-gain drug. It doesn’t increase fat storage or appetite. But it can cause temporary water retention, which feels like weight gain. It can also help you feel better-which might change your eating or activity habits in ways that affect the scale.
The key is to look at the whole picture. Track your symptoms. Rule out other causes. Don’t blame the drug without evidence. And if you’re unsure, talk to your doctor. They can help you decide whether the pain relief is worth the temporary bloating-or if another option might work better for your body.
Most people take mefenamic acid for just a few days a month. If you’re only using it during your period, any weight change is likely short-lived. Focus on how you feel-your energy, your pain levels, your quality of life. Those matter more than a number on the scale.
Can mefenamic acid cause long-term weight gain?
No, mefenamic acid does not cause long-term weight gain. Any weight increase is typically due to temporary fluid retention, which resolves once you stop taking the medication. Long-term use is not recommended due to risks of kidney, liver, or stomach issues, but these are unrelated to fat accumulation.
Does mefenamic acid affect metabolism?
There is no evidence that mefenamic acid slows down or speeds up metabolism. It does not interfere with thyroid function, insulin sensitivity, or fat-burning pathways. Any perceived change in energy or weight is likely due to reduced pain, improved sleep, or changes in diet and activity levels.
Is it safe to take mefenamic acid every month for periods?
It’s generally safe for short-term use during menstruation, but taking it every month for years increases the risk of gastrointestinal bleeding, high blood pressure, and kidney damage. Most doctors recommend limiting use to 3-7 days per cycle and considering hormonal options like birth control for long-term cramp management.
Can I lose the water weight from mefenamic acid quickly?
Yes. Reducing salt intake, drinking more water, and staying active can help your body shed excess fluid within 2-3 days after stopping the medication. Diuretics are not usually needed unless you have a medical condition like heart failure or kidney disease.
Why do some people say mefenamic acid made them gain weight?
Some people experience bloating or increased appetite after pain relief, which can lead to temporary weight gain. Others may confuse fluid retention with fat gain. Personal stories are common, but clinical data shows no direct link between mefenamic acid and fat accumulation. Individual responses vary, but the mechanism isn’t the drug itself-it’s how your body reacts to feeling better.
About Author
I'm William Thatcher, and I'm passionate about pharmaceuticals. I'm currently working as a pharmacologist, and I'm also researching the newest developments in the field. I enjoy writing about various medications, diseases, and supplements. I'm excited to see what the future of pharmaceuticals holds!
Sierra Thompson October 31, 2025
Mefenamic acid doesn't cause fat gain, but it absolutely can make you feel like you're drowning in your own skin. I gained 4 pounds in three days last cycle-rings wouldn't fit, face looked like a balloon. Cut the salt, drank a gallon of water a day, and it vanished in 48 hours. It's not the drug. It's your kidneys being grumpy because you're in pain and your body thinks it's under siege.
Stop blaming the pill. Start listening to your body.
Khaled El-Sawaf October 31, 2025
Let me be clear: anyone who attributes weight gain to mefenamic acid without controlling for sodium intake, baseline fluid retention, or behavioral changes post-pain-relief is engaging in pseudoscientific thinking. The study cited-a 2020 trial with 120 subjects-found only 8% sustained weight gain, and that was transient. The real issue is people mistaking physiological adaptation for pathology. This is why medicine is in crisis.
Correlation is not causation. And yet, here we are.