What is Metformin?

Metformin is a top medication choice for the treatment of Type 2 diabetes. It reduces blood glucose levels by inhibiting the production of hepatic (liver) glucose (gluconeogenesis). Recent studies have shown that metformin can increase insulin sensitivity, thereby helping the body’s cells to absorb the glucose from the blood.

This medication is typically well tolerated with minimal side effects. The more common and less severe side effects associated with the first use of metformin are:

  • Nausea
  • Diarrhea
  • Upset stomach
  • Metallic taste in the mouth

Long-term use is required for metformin to control blood glucose levels. Prolonged use of metformin can result in serious side effects that require immediate medical assistance.

Long-Term Side Effects of Metformin

Lactic Acidosis

The Food and Drug Administration (FDA) has issued a boxed warning for metformin, which is a severe form of notice given to a drug. The warning for metformin is due to lactic acidosis, a severe and life-threatening side effect.

Few scientific communities severely opposed this warning. They state that, even though there is the possibility of lactic acidosis with metformin, the incidence is scarce. A scientific study proved that there is no increase in lactic acid in the bloodstream of patients who have type 2 diabetes and kidney disease.

While there are many types of research being conducted regarding lactic acidosis due to metformin, it is important to know its symptoms. Lactic acidosis is a condition where there is an excess accumulation of lactate in the human body.

The lactic acid reduces the pH levels of blood, causing several other disorders. Most of the symptoms of lactic acidosis are related to its underlying cause.

Some of the most common symptoms of lactic acidosis are:

  • Cold hands or feet
  • Dizziness
  • Slow or irregular heartbeat
  • Weakness or tiredness
  • Unusual muscle pain
  • Trouble breathing
  • Feeling sleepy or drowsy
  • Stomach pain
  • Nausea or vomiting

If you have any of the symptoms mentioned above, consult your doctor immediately and seek emergency medical assistance.

Vitamin B12 Deficiency

Vitamin B12, also known as cobalamin, is a water-soluble vitamin required for growth and maturation of myelin sheath neurons, maturation of red blood cells (RBC), gene expression regulation, and fatty and amino acid synthesis.

The National Academy of Medicine recommends the following daily allotments of vitamin B12:

  • 4 micrograms/day (µg/day) for both men and women, aged 14 and up
  • 4 to 0.5 µg/day for neonates or infants from birth to 12 months of age
  • 9 to 18 µg/day for children between 1 and 13 years of age
  • 6 µg/day for pregnant women
  • 8 µg/day for lactating women

Metformin has been shown to inhibit the absorption of vitamin B12 with 29 weeks duration of metformin tablet usage. Controlled clinical trials have shown a decrease of normal serum vitamin B12 levels without clinical manifestations in approximately 7% of patients.

After an average of five years, the B12 reserves are depleted if there is no counterbalance from the diet.

Symptoms begin to manifest after this period:

  • Anemia
  • Constipation
  • Diarrhea
  • Muscle weakness
  • Nerve problems (tingling, numbness)
  • Vision problems

Metformin is known to interfere with calcium-dependent absorption of vitamin B12.

It is recommended to consume foods rich in vitamin B12 such as meat, eggs, dairy products, and fortified cereals. In case of severe deficiency, you may require additional supplements alongside the dietary vitamin.


While metformin is not a direct cause of hypoglycemia, it does play a role. As metformin reduces blood glucose levels, there is risk of hypoglycemia if you have:

  • Not eaten enough food
  • Taken other medications to reduce glucose
  • Consumed excess alcohol

All of these factors contribute to further reducing blood sugar levels, which can lead to hypoglycemia. You may experience sudden hunger, dizziness, weakness, and sweating.

To counteract this, consume foods that contain high amounts of glucose and are immediately absorbed into the bloodstream. A candy bar, fruit juice, and even sugar will help restore normal blood glucose levels.


Even though there are multiple side effects of metformin, it is still considered one of the best drugs available for treating diabetes. With some precautions, you can take this drug without any severe side effects.

Inform your doctor if you have a history of liver problems, myocardial infarction (MI), or kidney disease. Your doctor will change the dosage or even prohibit the use of metformin.

A healthy diet with multivitamin supplements, if needed, will keep you fit and in shape.

Doctor’s Recommendation

Metformin is usually well-tolerated but may cause nausea, diarrhea, and upset stomach at first, which often improve with time. Long-term use can lead to serious side effects like lactic acidosis, with symptoms such as cold extremities, irregular heartbeat, and muscle pain. Seek medical help if these occur.

Metformin can lower vitamin B12 levels, potentially causing anemia, weakness, and nerve issues. Eat foods rich in vitamin B12, like meat and dairy, and consider supplements if needed.

While Metformin doesn’t directly cause low blood sugar, it can increase the risk when combined with other medications, not eating enough, or drinking alcohol. Monitor your blood sugar closely and have fast-acting glucose ready. Regular check-ins with your healthcare provider are important for adjusting your dosage and managing health concerns.

You can buy Metformin online at canadianinsulin.com!

Disclaimer: Please note that the contents of this community article are strictly for informational purposes and should not be considered as medical advice. This article, and other community articles, are not written or reviewed for medical validity by Canadian Insulin or its staff. All views and opinions expressed by the contributing authors are not endorsed by Canadian Insulin. Always consult a medical professional for medical advice, diagnosis, and treatment.