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Biguanide (Type 2 Diabetes)

Metformin

Also sold as Glucophage

Long-term use reduces intestinal absorption of vitamin B12; folate status and CoQ10 demand may also decline.

This page provides educational information about possible medication-related nutrient relationships. It does not diagnose a deficiency, establish that this medication caused a symptom, or replace qualified medical care.
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Overview

About Metformin

Metformin belongs to the Biguanide (Type 2 Diabetes) class. Recognized brand names include Glucophage.

Long-term use reduces intestinal absorption of vitamin B12; folate status and CoQ10 demand may also decline.

MyDeficiencies does not provide dosing instructions, adverse-effect lists, or personalized medical advice. Always follow the guidance of your prescribing clinician and pharmacist.

Nutrient relationships

Possible Nutrient Relationships

  • Vitamin B12

    Stronger Evidence

    Cofactor for nerve myelination, red blood cell formation, and methylation.

    Available evidence suggests Metformin may affect vitamin b12 status. Individual responses vary.

  • Folate

    Moderate Evidence

    Supports DNA synthesis, methylation, and red cell production.

    Available evidence suggests Metformin may affect folate status. Individual responses vary.

  • CoQ10

    Emerging Evidence

    Mitochondrial electron transport and cellular ATP production.

    Available evidence suggests Metformin may affect coq10 status. Individual responses vary.

How to read this page

Evidence Strength

Evidence labels reflect the current strength of available research, not a guarantee of individual outcomes:

  • Stronger Evidence — Consistent, replicated evidence across multiple well-designed studies.
  • Moderate Evidence — Supportive evidence with some variability across populations or study designs.
  • Emerging Evidence — Early or mechanistic signals that warrant continued study.

Read our full evidence framework →

Proposed mechanisms

How These Relationships May Occur

Inhibits intestinal calcium-dependent B12 absorption and shifts gut microbiota toward Bacteroides-dominant profiles; modestly impairs Complex I of the mitochondrial electron transport chain.

A proposed mechanism explains how a relationship might occur. It does not prove that a clinically meaningful deficiency occurs in every individual.

Body systems

Body Systems That May Be Relevant

  • Digestive & Microbiome

    Moderate Evidence

    Effects on gut acidity, motility, or microbial composition may influence nutrient absorption.

  • Mitochondrial Energy

    Moderate Evidence

    Cofactors that support mitochondrial energy production may be relevant.

  • Oxygen & ATP

    Emerging Evidence

    Oxygen delivery and cellular energy metabolism may be relevant.

Symptoms and context

Symptoms and Context

Discussions around Metformin sometimes reference: Fatigue, Brain fog.

Symptoms such as fatigue, weakness, numbness, digestive changes, or mood changes can have many possible explanations. This page does not determine their cause.

Combinations reviewed

Reviewed Combinations

  • Metformin + Omeprazole

    Moderate Evidence

    Both reduce vitamin B12 absorption — PPI via acid suppression, metformin via ileal B12-IF complex interference. Effects are additive.

    Compounded risk of B12 deficiency with neurologic symptoms (paresthesias, balance, fatigue).

For your next visit

Questions You May Want to Discuss

  • Could Metformin affect any nutrients over time in my situation?
  • Are there symptoms or risk factors that would make further evaluation appropriate?
  • Could diet, other medications, or health conditions affect this relationship?
  • Would laboratory testing be clinically appropriate for me?
  • Are there medication or supplement interactions I should understand?

These are conversation starters, not recommendations to request a specific test, supplement, or medication change.

Research

Research and Sources

See our evidence methodology for how sources are evaluated.

View MyDeficiencies research updates(research revisions are tracked centrally, including for Metformin)
Related nutrients

Related Nutrients

  • Vitamin B12
    Stronger Evidence
  • Folate
    Moderate Evidence
  • CoQ10
    Emerging Evidence
Ready to go deeper

Explore Metformin in Your Report

Add Metformin to a MyDeficiencies analysis to view its reviewed nutrient relationships alongside other medications, supplements, symptoms, and relevant context.

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Educational only. Not a diagnosis. Not a substitute for qualified medical care.