Generic Metformin Benefits and Risks

One of the most commonly used drugs in the world, generic metformin is the first medicine[1] prescribed for nearly anyone with Type 2. Metformin is cheap because it’s available as a generic. You can buy a month’s supply at Walmart for $4. The top brand name in the United States is Glucophage, but few people need the brand name. Here are the pluses and minuses of metformin.

How metformin works

Like many great medicines, metformin started as a plant medicine. It was extracted from the French lilac plant (Galega officinalis). French lilac is a weed; people noticed that eating it made animals sick. When they investigated, they found that metformin was almost a wonder drug.


Metformin signals the liver to keep extra sugar in storage. Insulin sends the same vital message, but in Type 2 diabetes, the liver doesn’t listen to insulin. It dumps sugar instead of storing it. Metformin locks down the liver and so keeps glucose levels down.

Metformin also appears to reduce insulin resistance in the muscles. By making muscle cells more sensitive, it helps them take in more glucose. It may also slow the rate[2] at which glucose is absorbed into the blood.

Benefits of metformin

• Metformin lowers HbA1c (a measure of average glucose levels over the previous 2–3 months) by an average of 1.5% in people with Type 2 diabetes. If your A1c was 7.1%, above the ADA’s target range for people with diabetes, a 1.5% reduction would bring you to 5.6%, which is considered normal.

• Metformin reduces the risk of heart attack[3]. It does not cause weight gain, and some people find it helps with weight loss.

• Recent studies have suggested that metformin may slow[4] the aging process. This has been demonstrated in mice and worms, and a British study of 180,000 people found that, “Patients treated with metformin had a small but statistically significant improvement in survival compared with the cohort of non-diabetics, whereas those treated with sulfonylureas (another class of diabetes drug) had a consistently reduced survival compared with non-diabetic patients.”

• Metformin seems to prevent[5] or slow breast, prostate[6], liver, and colorectal cancer, according to several studies[7].

• In some research, the medicine seemed to slow or prevent Alzheimer’s disease[8], although a large study from Taiwan found the opposite.

• Metformin treats polycystic ovary syndrome (PCOS)[9] and is used as a fertility treatment.

• A Spanish study published last year in the journal Diabetes Care found that metformin encouraged the growth of good gut bacteria[10] that produce short-chain fatty acids (SCFA). SCFAs[11] protect against inflammation and reduce glucose levels.

Problems with metformin

Metformin irritates the stomach and intestines and can cause abdominal pain and severe vomiting or diarrhea. This side effect often goes away with time, but in some people, it doesn’t stop, and they have to quit taking it.

People combat these intestinal symptoms in several ways: They may try starting with a low dose and building up; switching to extended-release metformin pills; taking Pepto-Bismol or Metamucil; and exploring whether it’s better to take with food or without.

It’s usually better to take metformin with meals. Probiotics or cobiotics may control metformin’s abdominal side effects. If nothing works, tell your doctor. Metformin may not be right for you.

For years, there was concern that metformin might cause kidney damage. Research over the last 20 years has found no such risk[12], but doctors do not recommend metformin to people with severe kidney disease.

Taking metformin well

You might want to check your fasting blood sugars after taking metformin to see what dosing schedule works best for you. People may take anywhere from one to five doses a day. They may take extended-release metformin at different times and get different results. It’s worth experimenting.

According to the Food and Drug Administration (FDA), your doctor should order kidney function tests every year if you’re on metformin. You should also get your vitamin B12 level checked, because metformin can interfere with B12 absorption[13]. Don’t forget to ask.

Want to learn more about metformin? Read “Diabetes Medicine: Metformin,”[14] “What to Know About Metformin,”[15] and “Metformin: The Unauthorized Biography.”[16]

  1. first medicine:
  2. slow the rate:
  3. risk of heart attack:
  4. may slow:
  5. prevent:
  6. breast, prostate:
  7. several studies:
  8. Alzheimer’s disease:
  9. (PCOS):
  10. gut bacteria:
  11. SCFAs:
  12. no such risk:
  13. metformin can interfere with B12 absorption:
  14. “Diabetes Medicine: Metformin,”:
  15. “What to Know About Metformin,”:
  16. “Metformin: The Unauthorized Biography.”:

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David Spero: David Spero has been a nurse for 40 years and has lived with multiple sclerosis for 30 years. He is the author of four books: The Art of Getting Well: Maximizing Health When You Have a Chronic Illness (Hunter House 2002), Diabetes: Sugar-coated Crisis — Who Gets It, Who Profits, and How to Stop It (New Society 2006, Diabetes Heroes (Jim Healthy 2014), and The Inn by the Healing Path: Stories on the road to wellness (Smashwords 2015.) He writes for Diabetes Self-Management and Pain-Free Living (formerly Arthritis Self-Management) magazines. His website is His blog is

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