Metformin: Now or later?

Content provided by the Faculty of the Harvard Medical School

Metformin: Now or later?

Losing weight is the ideal way to deal with type 2 diabetes, the most common form of the disease. Just shedding 10 pounds or so will usually bring blood sugar levels back into the normal, healthy range.

The problem is that while many people can remain diet-and-exercise virtuous long enough to lose a few pounds — even 10 or so — most of us can't stay that way. The lost weight has a way of finding its way back home around our middles.

The American Diabetes Association's guidelines acknowledge that people have trouble keeping weight off. "Lifestyle interventions" to lose weight and get more active are step one in its guidelines. But the association also says that new patients should start taking metformin (Glucophage) right away because interventions usually don't work over the long haul. Metformin lowers blood sugar levels by decreasing the liver's production of sugar and by increasing the effectiveness of insulin, the hormone that escorts sugar into cells. Insulin resistance is one of the main features of type 2 diabetes. Cells start rebuffing the hormone, so sugar has nowhere to go. Levels in the blood start to climb.

Metformin is the first-line medication for several reasons. It's effective, lowering blood sugar levels by about 20%. People don't gain weight when they take it, in contrast to insulin and the sulfonylurea drugs (Diabeta, Micronase, Tolinase). And it's available as a generic, so it's relatively inexpensive. The most common side effects are gastrointestinal (a metallic taste in the mouth, nausea, diarrhea) and usually mild. In about a third of patients, the drug interferes with the absorption of vitamin B₁₂, but not so much that it causes anemia.

People with poor kidney function probably shouldn't take metformin because of the risk of lactic acidosis, the excessive buildup of lactic acid, a by-product of sugar metabolism. Diabetics are prone to developing kidney problems, so it's important that doctors monitor creatinine (pronounced cree-AT-i-nin) levels, which are an indicator of how well the kidneys are working. If levels start going up, another drug ought to be considered.

There's some controversy about whether we are turning to medications like metformin too soon. Proponents say they're being realistic about lifestyle changes and that these medications tame conditions that are deadly serious if they're allowed to progress. Critics counter that not nearly enough has been invested in devising ways to make diet and exercise programs work, especially in contrast to the billions spent on pharmaceutical research.

In any event, guidelines aren't supposed to suspend all thinking. If you've been diagnosed with diabetes, there's nothing wrong — and a lot right — with talking to your doctor about first trying a weight-loss program and exercise without metformin. If you go that route, it often helps to have a dietician involved. But you must also keep your eye on the prize: Bringing your blood sugar under control. The basic goal is a glycosylated hemoglobin (HbA1c) level under 7%. If you need metformin to reach it, stop fooling around and take the drug. You should start at a low dose (500 mg) and gradually increase the amount over a couple of months.

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Last updated:	August 03, 2007