Read the Medication Guide provided by your pharmacist before you start taking mefenamic acid and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth as directed by your doctor, usually 4 times a day. Take this medication with a full glass of water (8 ounces/240 milliliters) unless your doctor directs you otherwise. Do not lie down for at least 10 minutes after taking this medication. If stomach upset occurs while taking this medication, take it with food or milk. Do not take mefenamic acid with antacids unless directed by your doctor. Certain antacids may change the amount of mefenamic acid absorbed by the body.

The dosage and length of treatment are based on your medical condition and response to treatment. To reduce your risk of stomach bleeding and other side effects, take this medication at the lowest effective dose for the shortest possible time. Do not increase your dose or use this drug more often or for longer than prescribed. This medication usually should not be taken for more than 7 days at a time. Discuss the risks and benefits with your doctor or pharmacist.

If you are taking this drug "as needed" (not on a regular schedule), remember that pain medications work best if they are used as the first signs of pain occur. If you wait until the pain has worsened, the medicine may not work as well.

If you are using this medication for painful periods, take your first dose as soon as your period starts, or pain begins. Usually, you will only need to take it for the first 2 to 3 days of your period.

Tell your doctor if your condition lasts or gets worse.