B12 Side Effects Center

Last updated on RxList: 2/1/2022
B12 Side Effects Center

What Is B12?

B12 [vitamin b12 (liver-stomach concentrate with intrinsic factor)] is an anti-anemia preparation used to treat anemias that respond to oral hematinics, including pernicious anemia and other megaloblastic anemia and also iron-deficiency anemia. B12 is available in generic form.

What Are Side Effects of B12?

Side effects of B12 are uncommon but may include:

Dosage for B12

The dose of B12 is one capsule twice a day.

What Drugs, Substances, or Supplements Interact with B12?

B12 may interact with other drugs or supplements. Tell your doctor all medications and supplements you use.

B12 During Pregnancy or Breastfeeding

During pregnancy, B12 should be used only if prescribed. It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Additional Information

Our B12 [vitamin b12 (liver-stomach concentrate with intrinsic factor)] Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

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.


According to the USDA, there is no difference between a “portion” and a “serving.” See Answer
B12 Professional Information


Rarely, iron in therapeutic doses produces gastrointestinal reactions, such as diarrhea or constipation. Reducing the dose and administering it with meals will minimize these effects in the iron-sensitive patient.

In extremely rare instances, skin rash suggesting allergy has been noted following the oral administration of liver-stomach material. Allergic sensitization has been reported following both oral and parenteral administration of folic acid.

Read the entire FDA prescribing information for B12 (Liver-Stomach Concentrate With Intrinsic Factor)


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© B12 Patient Information is supplied by Cerner Multum, Inc. and B12 Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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