Before you begin using a medication, be sure to inform your doctor of any medical conditions or Allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use Omeprazole.

Diarrhea: When gastric acid is decreased, the number of bacteria normally in the digestive system increases. Occasionally, this can cause serious infection in the digestive tract. If you experience watery, foul-smelling bowel movements after starting to take omeprazole, contact your doctor as soon as possible.

Fluid and electrolyte balance: Omeprazole, like other PPIs, may cause the levels of electrolytes such as potassium, sodium, magnesium, chloride, and calcium in the blood to change while taking Omeprazole. If you experience symptoms of fluid and electrolyte imbalance such as muscle pains or cramps; dry mouth; numb hands, feet, or lips; or racing heartbeat, contact your doctor as soon as possible. Your doctor will do blood tests regularly to monitor the levels of these electrolytes in your blood while you are taking Omeprazole.

Liver function: Liver disease or reduced liver function may cause Omeprazole to build up in the body. If you have liver problems, discuss with your doctor how Omeprazole may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Omeprazole, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking Omeprazole. People with severe liver disease should generally not take more than 20 mg of omeprazole daily.

Methotrexate interaction: Omeprazole, like other medications in this group, may interact with methotrexate when the two medications are used at the same time. This combination may lead to higher than expected amounts of methotrexate in the body and can cause serious side effects, including kidney damage, irregular heartbeat, Anemia, or infection. If you take omeprazole and are also going to receive a dose of methotrexate, discuss with your doctor how Omeprazole may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Omeprazole, and whether any special monitoring is needed.

Osteoporosis-related fractures: Studies suggest that the use of omeprazole, like other PPIs, may be related to an increase risk of fractures, particularly for people who take Omeprazole for a year or longer. The lowest dose of Omeprazole to control the symptoms, taken for the shortest period of time is less likely to cause these problems.

Severe stomach problems: If you have recurrent vomiting, difficulty swallowing, blood in the stool, coughing up of blood, or significant unintentional weight loss, check with your doctor immediately. These symptoms may be signs of a more serious stomach problem.

Subacute cutaneous Lupus erythematosus (SCLE): Omeprazole, like other PPIs, has been rarely associated with SCLE, an autoimmune disease.  If you develop any skin lesions, especially in sun-exposed skin areas, and if accompanied by muscle aches or pains, contact your doctor immediately.

Vitamin B12: Long-term use of omeprazole may lead to vitamin B12 deficiency. If you are a vegetarian or have low vitamin B12 levels, discuss with your doctor whether any special monitoring is required.

Pregnancy: Omeprazole should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking Omeprazole, call your doctor immediately.

Breast-feeding: Omeprazole passes into breast milk. If you are a breast-feeding mother and are taking omeprazole, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using Omeprazole have not been established for children.