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Diabetes Mellitus and Vitamin B12

Updated: Aug 21, 2021

What is Diabetes Mellitus (DM)

Diabetes Mellitus is a chronic disease and if left untreated can lead to cardiovascular diseases, blindness, kidney disease, and lower-limb amputation. The disease can be treated with non-pharmacological methods such as education, medical nutrition therapy, exercise, and self-monitoring. When none pharmacologic interventions are insufficient, oral and injectable antidiabetes medication is added to achieve treatment goals.

Diabetes diagnosis

When an individual is diagnosed with pre-diabetes or type two diabetes and meets the criteria of BMI of ≥ 35 kg gm/m3. In addition to a family history of diabetes, elevated triglycerides, elevated LDL, reduced HDL cholesterol, and high blood pressure, the preferred initial medicinal treatment of this diagnosis is Metformin (1).


Metformin is used as the first line of pharmaceutical treatment for type 2 diabetes. It works by lowering blood glucose production in the liver and improving the body's sensitivity to insulin so that it can use insulin better. The use of metformin has also shown some positive effects on blood fat, causing a decrease in triglycerides, LDL cholesterol, and an increase in HDL (2). It also used for the treatment of infertility in women with polycystic ovarian syndrome (PCOS) as well as associated with a decreased risk in the occurrence of various cancers (3).

Metformin It is associated with weight loss due to gastrointestinal irritation or sometimes a loss of taste for food in some individuals, but it is not used for weight loss. Other side effects are nausea, bloating, flatulence, infrequent hypoglycemia in undernourished individuals, and vitamin B12 deficiency.

Vitamin B12

Vitamin B12 is also known as cobalamin. It is an important water-soluble vitamin and essential in the production of red blood cells, it helps to make DNA (the genetic material in all cells), as well as keeping the nervous system healthy. Vitamin B12 is found in animal foods such as fish, meat, poultry, eggs, and dairy products. Vitamin B12 deficiency can be caused by poor diet, atrophic gastritis, anemia, Crohn's disease, Celiac disease, lupus, and certain medication, which interferes with the absorption of vitamin B12.

Metformin and Vitamin B12 deficiency

Numerous research studies have proven that chronic use of metformin can result in vitamin B12 deficiency. Vitamin B12 deficiency causes hyperhomocysteinemia which increases the risk of retinopathy, macular edema, a neurological disorder such as cognitive, vascular, and vision impairment. In addition to psychiatric disorder, skin and, blood disorder (4). For most individuals, treatment with supplements resolves the problems but any nerve damage due to this deficiency can be permanent.

Prevention and treatment

Vitamin B12 deficiency can be prevented by eating an adequate amount of meat, fish, seafood, dairy products, and eggs. If you are a vegetarian and do not eat these products you can take vitamin B12 supplements or eat foods fortified with B12 such as cereals, nutritional yeast, almond milk, and soy milk. In severe cases, a B12 injection is given. For individuals with diabetes who take metformin, it is recommended to periodically check the status of vitamin B12 (5) and use supplements when clinically indicated to treat deficiency. The recommended daily allowance (RDA) for most individuals 14 years and older is 2.4 mcg, pregnant, breastfeeding women and older adults will need more (6)

Bottom line

Eating healthy, exercising and taking metformin are key factors in the management of type two diabetes. Metformin is also used in other treatments such as pre-diabetes, gestational diabetes, and PCOS. If you take metformin, routinely check your vitamin B12 levels and take supplements accordingly. Vitamin B12 supplements (7) can be taken along with eating adequate food sources that can prevent or treat this deficiency.

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