Metformin Interaction With Grapefruit

Our pharmacist answers the latest question regarding an interaction between metformin and grapefruit.


I am taking vitamin D supplement, Vitamin B12, and metformin for my Polycystic Ovarian Syndrome. I just want to know if there is any interactions with grapefruit. i have a high cholesterol that's why i included grapefruit on my diet. thank you so much.

Asked by Nick On Sep 25, 2017

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Sep 25, 2017

There is no interaction between any of the medications you mentioned in your question and grapefruit. It's a good thing that you ask since grapefruit can interact with so many different types of drugs!

We wrote extensively about the grapefruit interaction in one of our articles found here:

As we wrote, grapefruit can interact with medications in two ways. It can either interfere with the metabolizing enzyme known as CYP3A4 or it can interact with a drug transporter known as OATP. Metformin, vitamin D and vitamin B12 are not affected by changes in either CYP3A4 or OATP.

The only thing I would say is that SOMETIMES metformin can cause a decrease in absorption of vitamin B12 obtained through our diet so it is good that you are supplementing with it. Other than that possible minor interaction, you are good to go!

About the Pharmacist

Dr. Brian Staiger Pharm.D

Dr. Brian Staiger is a licensed pharmacist in New York State and the founder of He graduated from the University At Buffalo with a Doctor of Pharmacy degree in 2010. He has been featured in numerous publications including the Huffington Post as well as a variety of health and pharmacy-related blogs. Please feel free to reach out to him directly if you have any inquiries or want to connect! He's answered thousands of medication and pharmacy-related questions and he's ready to answer yours! Office: 716-389-3076

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