Common Diabetes Drug Metformin Linked to Vitamin B12 Deficiency

by DailyHealthPost Editorial

side effects of metformin

If you are taking the popular diabetes medication Metformin or know someone who does, please read on. Metformin is a common orally-administered drug used to treat type 2 diabetes.

side effects of metformin

It goes by other brand and generic names such as:

  • Glucophage
  • Riomet
  • Fortamet
  • Glumetza
  • Obimet
  • Dianben
  • Diabex
  • Diaformin

Approved in 1994, the way Metformin works is by increasing the individual’s sensitivity to her/his own insulin, reducing liver glucose production, and decreasing the amount of sugar absorbed by the intestines. (1)


Side Effects of Metformin

One of the problems with Metformin’s actions is that it causes vitamin B12 deficiency.

This side effect has been known since 2006. By way of the same mechanism that blocks sugar absorption by the intestines, this essential vitamin is also blocked. The extent of the deficiency is dose- and time-dependent: the higher the amount you take and the longer you take Metformin, the greater and more critical the deficiency.

Since 2006, there have been many studies into this Metformin/B12 relationship and all have come to the same conclusion. (2, 3)

In fact, a 2016 study conducted by the Albert Einstein College of Medicine in NY monitored the B12 levels of people taking a placebo and metformin twice a day for 5 and 13 years. Plus “Those who used to take metformin had lower levels of vitamin B12 in comparison to those who took the placebo.”(4)

In addition to a B12 deficiency, side effects of Metformin include pernicious anemia with long-term use. (5) The anemia is often preceded by neuropathy.

See also:Reversing diabetes Type-2


The Dangers Vitamin B12 Deficiency

It’s estimated that vitamin B12 affects roughly 15% of the general population (6). It’s estimated that up to 40% Americans also have dangerously low levels of the vitamin (7).

All eight B-complex vitamins are essential nutrients, obtained only through food. They help convert carbohydrates into fuel that the body can use and metabolize fats and proteins. Their actions contribute to proper nervous system function and are needed for healthy eyes, liver, hair, and skin.

Vitamin B12 is sometimes referred to as “the happy vitamin” because it affects mood. B12 is special among the B-complex vitamins because it is involved in the production of RNA and DNA—our genetic material.

Along with vitamin B9 (folic acid), B12 also helps to create red blood cells and facilitates the use of iron in the body. It’s also instrumental in brain function and memory; deficiency is associated with the risk of Alzheimer’s disease. (8, 9)

Other processes in which B12 is involved include:

  • bone health (10)
  • digestion
  • hormone production
  • immune system support
  • circulation
  • reproductive health
  • cognition (11)

Metformin and Heart Disease

Diabetes and heart disease often go together. The inability of cells to properly metabolize sugar and the resulting excess in the body have direct and indirect effects on the vascular “tree”. The consequences of diabetes on the circulatory system are macrovascular (coronary artery disease, stroke, peripheral arterial disease) and microvascular (neuropathy, retinopathy, and nephropathy) in nature. Because of vitamin B12’s role in the formation of red blood cells and circulatory support, long-term use of Metformin increases the risk of microvascular deterioration. (12)


One study found that lifestyle changes along with discontinuance of diabetes treatment with Metformin were equally effective at reducing the risk of developing diabetes than taking Metformin. Furthermore, in women, the risk of developing diabetes was lower with lifestyle intervention than with the use of Metformin. (13)

Read more: how to control blood sugar levels

Signs of B12 Deficiency

B12 deficiency can manifest itself in following ways (14,15,16,17):

  • Anemia, megaloblastic anemia, and pernicious anemia
  • Loss of balance and confusion
  • Numbness or tingling in the arms and legs
  • Weakness
  • Constipation, diarrhea, a loss of appetite, or gas
  • Nerve problems like numbness or tingling, muscle weakness, and problems walking
  • Vision loss
  • Mental health problems (including psychosis and depression)
  • Dementia
  • Alzheimer’s
  • Heart disease

A simple blood test can diagnose a vitamin B12 deficiency. If you experience one or more the symptoms above, it’s time to give your doctor a call.

Getting Enough B12

It’s recommended that you actively monitor vitamin B12 levels if taking any diabetes medication. While you can take B12 supplements, most of them are synthetic and aren’t as effective as B12 found naturally in foods. Vitamin B12 can be found in abundance in meat and fish; unfortunately for vegetarians and vegans, plant sources aren’t readily found and it takes a conscious effort to increase your intake.

Foods that contain significant amounts of B12 include:

  • fish: mackerel, salmon, tuna, cod, sardines, scallops, shrimp, clams, oysters
  • meat: beef and other red meat, poultry
  • cow’s milk
  • cheese
  • yogurt
  • eggs

Vegan foods with lesser amounts of B12 include:

The recommended daily amount (RDA) of vitamin B12 increases as you get older. (19) It’s recommended that vegans take even more than the RDA of B12 to compensate for lower bioavailability of supplements and lack of animal sources in their diets. The supplemental form of B12 most readily absorbable is methylcobalamin.

Keep in mind that your body only absorbs 50% of the vitamin B12 it absorbs. What’s more, certain medical conditions, such as gut inflammation can impede B12 absorption, so it’s important to monitor your levels as you adjust your diet or begin supplementation.

If you have type 2 diabetes, it can be controlled to a great extent by diet and lifestyle. Consult your doctor or naturopath about feasible alternatives to medication. If you do take medication, ask that your B12 is regularly checked to ensure you’re getting enough of this essential vitamin.