Quick answer

Ask your pharmacist or doctor before combining. Stomach acid releases vitamin B12 from food, and proton pump inhibitors reduce that acid. The omeprazole label says daily use of any acid-suppressing medicine for a long time, such as more than 3 years, may lead to poor B12 absorption, and NIH names these medicines as a cause of low B12.^1,2

Key facts

NIH says gastric acid inhibitors, including proton pump inhibitors, can interfere with B12 absorption from food by slowing the release of stomach acid, which can lead to B12 deficiency.^2,3
The omeprazole label says daily use of any acid-suppressing medicine over a long period, such as longer than 3 years, may lead to poor B12 absorption, and describes reports of deficiency as rare.¹
NIH says B12 added to supplements and fortified foods is already in free form, so it does not need the step that stomach acid performs for B12 in food.³
MedlinePlus asks people to tell their doctor before taking omeprazole if they have ever had low vitamin B12.⁴
NIH says 3% to 43% of older adults have low B12, and that many older adults do not make enough stomach acid to release B12 from food.²

Your doctor may want to check on you

Proton pump inhibitors such as omeprazole and lansoprazole reduce stomach acid, which the body needs to release B12 from food. The omeprazole label says daily use of any acid-suppressing medicine for a long time, such as more than 3 years, may lead to poor absorption of B12.^1,2,3

On the medicine's label

Why do proton pump inhibitors cause low vitamin B12?

NIH describes absorbing B12 from food as a two-step process. First, hydrochloric acid in the stomach separates B12 from the protein it is attached to. Then the freed B12 combines with intrinsic factor, a protein made by the stomach, and the two are absorbed together. MedlinePlus describes these medicines as lowering the acid the stomach makes, and NIH says that can interfere with the first step.^2,3,4

The omeprazole label gives the time scale. Daily treatment with any acid-suppressing medicine over a long period, for example longer than 3 years, may lead to malabsorption of B12 caused by low or absent stomach acid. The label adds that rare reports of B12 deficiency have appeared in the medical literature, and that the diagnosis should be considered if symptoms of low B12 appear in a person taking omeprazole.¹

Is the B12 in a supplement affected by acid reducers?

B12 in supplements is not attached to protein, so it does not need stomach acid to be released, but it still has to combine with intrinsic factor to be absorbed.²

NIH's health professional sheet says the same thing in other words: B12 added to fortified foods and dietary supplements is already in free form and does not require the separation step. Neither NIH sheet says what that means for a person who has taken an acid reducer for years. Whether you need a blood test or a supplement, and in which form, is a question for your doctor.³

Who else has trouble absorbing B12 from food?

NIH says many older adults do not have enough stomach acid to release the B12 in food, and that between 3% and 43% of older adults have low B12, depending on how it is measured. Other groups it names include people with pernicious anemia or atrophic gastritis, people who have had stomach or bowel surgery, and people who follow vegetarian or vegan diets. An acid reducer is one more factor to mention to your doctor.^2,3

Do H2 blockers and other acid reducers count too?

Your doctor may want to check on you

H2 blockers such as cimetidine also reduce stomach acid and can interfere with absorbing B12 from food, which NIH says can lead to low B12.^2,3

Reported in studies

NIH groups proton pump inhibitors and H2 blockers together as gastric acid inhibitors, so the question covers both. It also lists metformin, a diabetes medicine, as another medicine that can lower B12.³

What are the signs of low B12 to mention?

NIH lists fatigue, nerve changes, tongue changes (glossitis), palpitations and low blood cell counts among the signs of B12 deficiency, and says symptoms can take several years to appear. Tell your doctor about these rather than guessing the cause.³

Doctors usually check B12 with a blood test, and a second test for methylmalonic acid is used to confirm a borderline result.³

What to ask your pharmacist about B12 and an acid reducer

How long have I taken this acid reducer, and has my B12 ever been checked?
Is my acid reducer a proton pump inhibitor or an H2 blocker?
Does my multivitamin or B12 product already contain B12, and in what form?
Do I take metformin or another medicine that can lower B12?

Bring the labels of your acid reducer and of any multivitamin or B12 product, so your pharmacist can see everything at once.

Questions people ask

Can proton pump inhibitors cause vitamin B12 deficiency?

NIH says acid-reducing medicines can interfere with B12 absorption from food and lead to deficiency. The omeprazole label points to daily use over a long period, such as longer than 3 years, and describes reports of deficiency as rare.^1,2

Why do proton pump inhibitors cause vitamin B12 deficiency?

They decrease stomach acid, and stomach acid is what separates B12 from the protein in food. With less acid, less B12 is released from food to be absorbed.^2,4

Is vitamin B12 deficiency common with proton pump inhibitors?

The sources checked give no percentage for people taking these medicines. The label calls reports of deficiency rare, and NIH says acid reducers can lead to it.^1,3

Should I take vitamin B12 with a proton pump inhibitor?

The sources checked do not give advice to start a supplement. NIH explains that B12 in supplements is already free of food protein, and the label says to consider the diagnosis if symptoms appear. Ask your doctor whether a blood test makes sense.^1,3

See what we make

Every product shows its whole label and what its lab report covers. The store opens soon.

See the Full Measure line

Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.