You may recall that I recently wrote a series on various medicines and how they can affect your diabetes (see "The Ups and Downs of Meds and Diabetes [Part 1]" as well as Part 2, Part 3, Part 4, and Part 5). One kind reader, who happens to be a nurse, asked me to devote a post to metformin with regard to its effects on kidneys and special considerations to keep in mind with this drug.
I wrote about metformin back in December 2006 (was it that long ago?) and its link to vitamin B12 deficiency (see “Metformin and Risk For Vitamin B12 Deficiency”). But there are other important facts to know about this very popular diabetes drug.
Raise your hand if you take metformin. OK, obviously I can’t see you, but I’ll wager that many of you reading this are on this medication. Metformin is the generic name for Glucophage, Glucophage XR, Glumetza, Fortamet, and Riomet. It also comes combined with other diabetes medications, including glyburide (in Glucovance), glipizide (in Metaglip), rosiglitazone (in Avandamet), pioglitazone (in Actoplus Met), sitagliptin (in Janumet), and repaglinide (in PrandiMet).
I’ve read that approximately 35 million prescriptions were written for metformin in 2006, making this one of the top 10 best selling generic drugs. And you may not be aware that the American Diabetes Association, in its 2006 practice guidelines for health-care professionals, recommended metformin over sulfonylureas as the first drug of choice for people with Type 2 diabetes. This really isn’t surprising. Metformin has a long track record for being safe and causing relatively few serious side effects—plus, it also works! Chances are, if you have Type 2 diabetes and need to start on medication, your health-care provider will recommend you take metformin.
How It Works
Just a quick review in case you’re not sure what metformin does. Metformin works by:
- Reducing the amount of glucose released by your liver (and your liver regularly releases glucose); and
- Helping the insulin in your body work better (i.e., increasing insulin sensitivity).
Metformin doesn’t cause your pancreas to secrete insulin, as do sulfonylureas, so it’s very unlikely that you will experience hypoglycemia (low blood glucose) with metformin alone; however, if you take a sulfonylurea or insulin along with metformin, you may get hypoglycemia.
Side effects are usually temporary, and consist of gas, nausea, vomiting, and/or diarrhea. Some people have side effects, some never do. And if you can “stomach” metformin for the first month or so, you may end up losing weight (another benefit for many people).
Metformin isn’t meant for people with Type 1 diabetes, although it has been known to be given “off label” to people with Type 1 who also have insulin resistance.
Things To Keep in Mind
Lactic acidosis: Lactic acidosis is a rare but extremely serious condition that occurs in about 1 out of every 30,000 people who take metformin. Symptoms include weakness, shortness of breath, abdominal pain, and muscle pain. People at increased risk for lactic acidosis include those with kidney or liver problems, congestive heart failure, alcohol abuse, or dehydration. Lactic acidosis may also occur if metformin is taken during X-rays with dye and surgery; for this reason, metformin usually needs to be stopped 48 hours before these procedures. Always talk with your health-care provider if you take metformin and are scheduled for an X-ray, CAT scan, or for surgery.
In addition, metformin should not be used in people with a creatinine clearance of less than 30 ml/minute, and used with great caution if the creatinine clearance is between 30 and 50 ml/minute (creatinine clearance is a test that measures how well your kidneys are working). So, if you have diabetic kidney disease, metformin may not be the first drug of choice for you.
Irregular menstrual periods: Metformin is used to induce ovulation in women with polycystic ovary syndrome (PCOS), a condition that can lead to an irregular menstrual cycle.
Gestational diabetes Metformin is now deemed to be safe in women with gestational diabetes. Women with gestational diabetes traditionally had to take insulin during their pregnancy. Metformin (and also glyburide, brand names Micronase, DiaBeta, and Glynase), are now two other options.
Prediabetes: Although not formally approved by the U.S. Food and Drug Administration (FDA), metformin has been given with success to people who have prediabetes, and, in fact, was used in a major study called the Diabetes Prevention Program to help prevent diabetes.
Children: The incidence of Type 2 diabetes in children is escalating, and while, of course, lifestyle changes are critical, metformin should be the first drug of choice, if indicated.
One of the physicians I work with calls metformin the “best medication for treating Type 2 diabetes.” So, if you are one of the many who take metformin, I hope that’s the case for you!