Omeprazole is used to treat symptoms of gastroesophageal reflux disease (GERD) and other conditions caused by excess stomach acid. Omeprazole is also used to promote healing of erosive esophagitis (damage to your esophagus caused by stomach acid).

Omeprazole may also be given together with antibiotics to treat gastric ulcer caused by infection with Helicobacter pylori (H. pylori).

Over-the-counter (OTC) omeprazole is used in adults to help control heartburn that occurs 2 or more days per week. This medicine not for immediate relief of heartburn symptoms. OTC omeprazole must be taken on a regular basis for 14 days in a row.

Omeprazole may also be used for purposes not listed in this medication guide.

Heartburn can mimic early symptoms of a heart attack. Get emergency medical help if you have chest pain that spreads to your jaw or shoulder and you feel sweaty or light-headed.

You should not use omeprazole if you are allergic to it, or if:

• you are also allergic to medicines like omeprazole, such as esomeprazole, lansoprazole, pantoprazole, rabeprazole, Nexium, Prevacid, Protonix, and others;
• you had breathing problems, kidney problems, or a severe allergic reaction after taking omeprazole in the past; or
• you also take HIV medication that contains rilpivirine (such as Complera, Edurant, Odefsey, Juluca).

Ask a doctor or pharmacist if this medicine is safe to use if you have:

• trouble or pain with swallowing;
• bloody or black stools, vomit that looks like blood or coffee grounds;
• heartburn that has lasted for over 3 months;
• frequent chest pain, heartburn with wheezing;
• unexplained weight loss;
• nausea or vomiting, stomach pain;
• liver disease;
• low levels of magnesium in your blood; or
• osteoporosis or low bone mineral density (osteopenia).

You may be more likely to have a broken bone in your hip, wrist, or spine while taking a proton pump inhibitor long-term or more than once per day. Talk with your doctor about ways to keep your bones healthy.

Ask a doctor before using this medicine if you are pregnant or breastfeeding.

Do not give this medicine to a child without medical advice.

Use FIRST Omeprazole (Oral) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop using omeprazole and call your doctor at once if you have:

• severe stomach pain, diarrhea that is watery or bloody;
• new or unusual pain in your wrist, thigh, hip, or back;
• seizure (convulsions);
• kidney problems--fever, rash, nausea, loss of appetite, joint pain, urinating less than usual, blood in your urine, weight gain;
• low magnesium--dizziness, irregular heartbeats, feeling jittery, muscle cramps, muscle spasms, cough or choking feeling; or
• new or worsening symptoms of lupus--joint pain, and a skin rash on your cheeks or arms that worsens in sunlight.

Taking omeprazole long-term may cause you to develop stomach growths called fundic gland polyps. Talk with your doctor about this risk.

If you use omeprazole for longer than 3 years, you could develop a vitamin B-12 deficiency. Talk to your doctor about how to manage this condition if you develop it.

Common side effects may include:

• cold symptoms such as stuffy nose, sneezing, sore throat (especially in children);
• fever (especially in children);
• stomach pain, gas;
• nausea, vomiting, diarrhea; or
• headache.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

This medicine can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or bloody, call your doctor before using anti-diarrhea medicine.