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How soon after taking levothyroxine can I take omeprazole?

Medically reviewed by Sally Chao, MD. Last updated on Oct 1, 2021.

Official answer


There is a known drug interaction between levothyroxine and omeprazole, but the timing of when you take the two medicines is not relevant. Omeprazole decreases the absorption of your thyroid medication. If you need to be on a course of omeprazole while taking levothyroxine, your doctor may order more frequent laboratory testing to confirm you are absorbing enough levothyroxine.

Omeprazole decreases the amount of acid produced by your stomach. It is dosed once a day. Its effects of decreasing stomach acid begin within an hour and last as long as 72 hours. After the drug is stopped, normal levels of stomach acid return in 3 to 5 days.

Levothyroxine should be taken once a day in the morning on an empty stomach (30 to 60 minutes before eating breakfast). Taking it on an empty stomach results in the best absorption from the intestine. It also requires the presence of stomach acid for the best absorption.

Because omeprazole reduces the amount of acid produced by your stomach, it results in decreased absorption of levothyroxine. Since the acid reduction effects of omeprazole last more than 24 hours, altering the time either medication is taken will not avoid the drug-drug interaction. If you take omeprazole to treat heartburn, make sure you inform your doctor. You may need to have your thyroid hormone levels checked more frequently and your dose of levothyroxine adjusted.


Omeprazole has been used to treat different gastrointestinal disorders. It was first available only as a prescription medicine and was approved for the treatment of stomach and intestinal ulcers and for gastroesophageal reflux disease (GERD). For these purposes, courses of therapy range from 4 to 8 weeks. In 2003, omeprazole became available without a prescription to treat heartburn. When treating heartburn, omeprazole should not be taken for more than 14 days at a time.


Levothyroxine is a synthetic version of the thyroid hormone T4. With hypothyroidism, you do not produce enough thyroid hormone and must replace it. This replacement therapy is needed for your lifetime. The effectiveness of levothyroxine therapy is measured by monitoring your symptoms and by checking the amount of two key thyroid-related hormones, thyroid stimulating hormone and T4, in the blood.

Levothyroxine interacts with many other medications, but there are different kinds of drug interactions. Depending on the drug, you may need to avoid the drug, avoid taking it at certain times or be monitored by your physician.

  1. U.S. Food and Drug Administration (FDA). Synthroid. Last updated July 2020. Available at: [Accessed August 19, 2021].
  2. U.S. Food and Drug Administration (FDA). Prilosec. Last updated October 2016. Available at: [Accessed August 25, 2021].
  3. U.S. Food and Drug Administration (FDA). Prilosec OTC. Last updated January 2020. Available at: [Accessed August 25, 2021].

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