metformin, carcinogen, NDMA

Could Metformin Contain a Carcinogen?

Metformin is a drug commonly prescribed for type 2 diabetes to lower blood sugar. New reports have surfaced that it may contain the carcinogen N-Nitrosodimethylamine, or NDMA.

The FDA is testing metformin samples for the carcinogen. After testing, the FDA may issue recalls, which would be devastating to many people with diabetes, for which there is not another drug like metformin. 

People who are currently taking metformin should not stop taking the medication until speaking with their doctors. 

Popular heartburn medication Zantac (ranitidine) was recalled for containing the same carcinogen in September. In addition, common blood pressure medications angiotensin II receptor blockers (ARBs) were recalled in several countries due to containing NDMA.

What is NDMA?

NDMA can form during the process of making, packaging, and storing a drug in an industrial facility. It is called a genotoxic substance because it can harm the genetic material in a cell, and, over time, increase cancer risk.

NDMA is safe in levels below 96 nanograms daily, but amounts higher than that are dangerous.

The European Medicines Agency has not detected dangerous levels in metformin in the EU. However, in Singapore, three versions of metformin were recalled due to high NDMA levels.


About metformin

Metformin is the most widely-prescribed drug for diabetes. Over 120 million people around the world have been prescribed the drug, sometimes for uses other than diabetes.

The drug, also known as glucophage, helps people with diabetes manage their blood sugar levels. It does this by inhibiting glucose production in the liver, and reducing the amount of sugar the body makes and absorbs.

In addition, metformin increases insulin sensitivity. The drug works best as part of a larger health regimen in which the person with diabetes also follows a healthy eating plan and exercises regularly.

Metformin interactions

Metformin may interact with medications for:

  • Blood pressure 
  • Cholesterol 
  • Glaucoma 
  • Digestion 
  • Hormone 
  • Tuberculosis 
  • Thyroid 

Metformin may also interact with some vitamins and supplements meant to decrease blood sugar. If you take medications for any of these conditions, talk with your doctor or pharmacist about possible interactions with the drugs.


When you shouldn’t take metformin

There are some cases in which you should NOT take metformin, such as:

  • If you have kidney or liver issues
  • If you have had a heart attack or acute heart failure
  • If you drink alcohol often or in large quantities

When starting on metformin, begin with a small dose and gradually move up to avoid gastric issues. Always take it with food. While metformin is generally known as a safe and very effective drug, consult your doctor with any problems that might arise when taking metformin.