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Dynamic Chiropractic – August 12, 2010, Vol. 28, Issue 17

Metformin: Common Drug-Nutrient Interactions

If any of your patients are taking this drug for blood sugar control, you need to know how certain supplements can impact its effectiveness.

By Todd Mexico, DC and Brandon Blood, DC

The topic of drug-nutrient interactions is becoming increasingly popular, even reaching national television.

"The Dr. Oz Show" recently spotlighted this subject.1 It also needs to become increasingly popular in terms of our patient care. Chiropractors, nutritionists, pharmacists, medical doctors and others all have the responsibility to protect patients from negative drug-nutrient interactions, as well as provide better patient care by recommending nutritional supplementation that could enhance patient health and well-being, particularly for those taking medication.

As we continue our educational series on the importance of understanding drug-nutrient interactions, let's dissect metformin, a drug commonly used to control blood sugar levels in patients with type 2 diabetes.2 According to, 7.8 percent of Americans have diabetes, with 1.6 million new cases diagnosed every year.3 In 2006, diabetes was listed as the seventh leading cause of death in the United States.

When it comes to potential drug-nutrient interactions, especially relative to metformin, one most understand pharmacodynamic interactions between drugs and nutrients that may be additive or synergistic in nature. A different example to further explain this is coumadin and fish oil. Both are blood thinners and when consumed together, have a synergistic outcome. There are several supplements that have positive effects on decreasing blood-sugar levels. Although this is desirable, it can potentially lead to hypoglycemia, an equally undesirable outcome if not managed correctly. For the purpose of this article, all synergistic interactions will be considered negative for this reason.

Potential Positive Supplement Interactions With Metformin

  • Vitamin B12: Consuming vitamin B12 while on metformin may combat B12 malabsorption/deficiency, as metformin is known to decrease B12 levels.4-6
  • Omega-3 fatty acids: Consuming omega 3 EFAs may help reduce hypertriglyceridemia and heart disease associated with diabetes.7-10
  • CoQ10: Consuming CoQ10 may improve blood sugar control as well as combat reduced CoQ10 production, as metformin is known to decrease CoQ10 production.11-13

Potential Negative Supplement Interactions With Metformin

  • Chromium: May help improve blood sugar control,14-16 which, when consumed with metformin, may ultimately lead to low blood sugar levels. Should be medically co-managed.
  • Cocoa (Theobroma cacao): May decrease the effect of metformin, causing potentially undesirable effects in patients dependent on the drug for blood sugar control.17
  • Fenugreek (Trigonella sp.): As with chromium, may improve blood sugar control, which, when consumed with metformin, may ultimately lead to low blood sugar levels. Should be medically co-managed.18,19

The findings above are not inclusive of the potential drug-nutrient interactions with metformin; they are just a sample of the information that has been researched. It is important for chiropractors to analyze all medications and nutritional supplements their patients are taking for possible interactions. It is perhaps equally important to document these results in a manner that exhibits due diligence from a medical-legal standpoint. By understanding this research and applying your nutritional knowledge in practice, you will likely also see an increase in patient confidence in the care you provide.


  1. "Mixing Medicines Is Risky Business."
  2. Becker ML, et al. Genetic variation in the multidrug and toxic extrusion 1 transporter protein influences the glucose-lowering effect of Metformin in patients with diabetes. Diabetes, March 2009.
  3. American Diabetes Association. Diabetes statistics.
  4. Adams JF, et al. Malabsorption of vitamin B12 and intrinsic factor secretion during biguanide therapy. Diabetologia, 1983;24(1):16-8.
  5. Ting RZ, Szeto CC, Chan MH, et al. Risk factors of vitamin B12 deficiency in patients receiving metformin. Arch Intern Med, 2006;166:1975-9.
  6. Pflipsen, et. al. The prevalence of vitamin B12 deficiency in patients with type 2 diabetes: a cross-sectional study. J Am Board Fam Med, 2009;22:528-34.
  7. Schectman G, Kaul S, Kissebah AH. Effect of fish oil concentrate on lipoprotein composition in NIDDM. Diabetes, 1988;37:1567-73.
  8. Sheehan JP, Wei IW, Ulchaker M, Tserng KY. Effect of high fiber intake in fish oil-treated patients with non-insulin-dependent diabetes mellitus. Am J Clin Nutr, 1997;66:1183-7.
  9. Friedberg CE, Janssen MJ, Heine RJ, Grobbee DE. Fish oil and glycemic control in diabetes: a meta-analysis. Diabetes Care, 1998;21:494-500.
  10. Toft I, Bonaa KH, Ingebretsen OC, et al. Effects of n-3 polyunsaturated fatty acids on glucose homeostasis and blood pressure in essential hypertension: a randomized, controlled trial. Ann Intern Med, 1995;123:911-8.
  11. Kishi T, et al. Bioenergetics in clinical medicine. XI. Studies on CoQ and diabetes mellitus. J Med, 1976;7(3-4):307-21.
  12. Hodgson JM, Watts GF, Playford DA, et al. Coenzyme Q(10) improves blood pressure and glycaemic control: a controlled trial in subjects with type 2 diabetes. Eur J Clin Nutr, 2002;56:1137-42.
  13. Singh RB, Niaz MA, Rastogi SS, et al. Effect of hydrosoluble coenzyme Q10 on blood pressures and insulin resistance in hypertensive patients with coronary artery disease. J Human Hypertens, 1999;13:203-8.
  14. Anderson RA, Cheng N, Bryden NA, et al. Elevated intakes of supplemental chromium improve glucose and insulin variables in individuals with type 2 diabetes. Diabetes, 1997;46:1786-91.
  15. Mertz W. Interaction of chromium with insulin: a progress report. Nutr Rev, 1998;56:174-7.
  16. Porter DJ, Raymond LW, Anastasio GD. Chromium: friend or foe. Arch Fam Med, 1999;8:386-90.
  17. Boullata J. Natural health product interactions with medication. Nut Clin Pract, 2005.
  18. Sharma RD, Raghuram TC, Sudhakar Rao N. Effect of fenugreek seeds on blood glucose and serum lipids in type 1 diabetes. Eur J Clin Nutr, 1990;44:301-6.
  19. Sharma RD, Sarkar A, Hazara DK, et al. Use of fenugreek seed powder in the management of non-insulin dependent diabetes mellitus. Nutr Res, 1996;16:1131-9.

Dr. Todd Mexico is 2006 graduate of Palmer College of Chiropractic Florida and co-founder of Dr. Mexico practices in Baldwinville, Mass.

Dr. Brandon Blood is 2006 graduate of Palmer College of Chiropractic Florida and co-founder of Dr. Blood maintains a practice in Canton, Ohio.

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