What are oral hypoglycemics? How do they interact with other drugs?

Quick Answer
Medications used for controlling blood sugar in persons with type 2 diabetes.
Expert Answers
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Vitamin B12

Effect: Supplementation Possibly Helpful

The biguanide oral hypoglycemic drugs metformin and phenformin can cause malabsorption of vitamin B12 . In turn, this can lead to vitamin B12 deficiency. Taking vitamin B12 supplements should easily solve this problem.

Coenzyme Q10 (CoQ10)

Effect: Possible Benefits and Risks

Studies suggest that the oral hypoglycemic drugs glyburide, phenformin, and tolazamide may inhibit the normal production of the substance CoQ10. While there is no direct evidence that taking extra CoQ10 will provide any specific benefit, supplementing with CoQ10 on general principle might make sense.

In addition, there is some evidence that the use of CoQ10 could improve blood sugar control for persons with diabetes. However, one might also need to reduce one’s medication dosage.


Effect: Might Require Reduction in Medication Dosage

There is some evidence that the supplement ipriflavone might increase blood levels of oral hypoglycemic drugs. This could lead to a risk of blood sugar levels falling too low. Persons taking oral hypoglycemic medications should not take ipriflavone without first consulting a physician.


Effect: Might Require Reduction in Medication Dosage

Magnesium supplements might increase the absorption of chlorpropamide (and, by inference, other oral hypoglycemics), possibly requiring a dosage reduction.

Herbs and Supplements

Effect: Might Require Reduction in Medication Dosage

Meaningful preliminary evidence suggests that the use of the following herbs and supplements could potentially improve blood sugar control and thus require a reduction in daily doses of oral hypoglycemic medication: aloe, chromium, fenugreek, ginseng, gymnema, and vanadium.

Weaker evidence suggests that the following herbs and supplements could potentially have the same effect under certain circumstances: Anemarrhena asphodeloides, arginine, Azadirachta indica, bilberry leaf, biotin, bitter melon, carnitine, Catharanthus roseus, Coccinia indica, CoQ10, conjugated linoleic acid, Cucumis sativus, Cucurbita ficifolia, Cuminum cyminum (cumin), Euphorbia prostrata, garlic, glucomannan, Guaiacum coulteri, Guazuma ulmifolia, guggul, holy basil, Lepechinia caulescens, lipoic acid, Medicago sativa (alfalfa), Musa sapientum L. (banana), niacinamide, nopal cactus, onion, Phaseolus vulgaris, Psacalium peltatum, Pterocarpus, Rhizophora mangle, salt bush, Spinacea oleracea, Tournefortia hirsutissima, Turnera diffusa, and vitamin E.

Potassium Citrate

Effect: Possible Harmful Interaction

Potassium citrate and other forms of citrate (such as calcium citrate and magnesium citrate) may be used to prevent kidney stones. These agents work by making the urine less acidic. This effect on the urine may lead to decreased blood levels and therapeutic effects of chlorpropamide and possibly other oral hypoglycemic drugs. For this reason, it may be advisable to avoid these citrate compounds during treatment with oral hypoglycemic drugs.

Ginkgo biloba

Effect: Possible Harmful Interactions

It has been suggested that ginkgo might cause problems for persons with type 2 diabetes, both by altering blood levels of medications and by directly affecting the blood-sugar-regulating system of the body. However, the most recent and best-designed studies have failed to find any such actions. Until this situation is clarified, people with diabetes should use ginkgo only under physician supervision.

Dong Quai, St. John’s Wort

Effect: Possible Harmful Interaction

Some oral hypoglycemic drugs have been reported to cause increased sensitivity to the sun, amplifying the risk of sunburn or skin rash. Because St. John’s wort and dong quai may also cause this problem, taking these herbal supplements during treatment with oral hypoglycemic drugs might add to this risk. It may be a good idea to wear sunscreen or protective clothing during sun exposure if one takes any of these herbs while using an oral hypoglycemic medication.


Hodgson, J. M., et al. “Coenzyme Q(10) Improves Blood Pressure and Glycaemic Control: A Controlled Trial in Subjects with Type 2 Diabetes.” European Journal of Clinical Nutrition 56 (2002): 1137-1142.

Kudolo, G. B., et al. “Short-Term Ingestion of Ginkgo biloba Extract Does Not Alter Whole Body Insulin Sensitivity in Non-diabetic, Pre-diabetic, or Type 2 Diabetic Subjects.” Clinical Nutrition 25 (2006): 123-134.

Pronsky, Z. M., and J. P. Crowe. Food Medication Interactions. 16th ed. Birchrunville, Pa.: Food-Medication Interactions, 2010.

Ting, R. Z., et al. “Risk Factors of Vitamin B12 Deficiency in Patients Receiving Metformin.” Archives of Internal Medicine 166 (2006): 1975-1979.