Metformin is one of the most commonly prescribed drugs for type 2 diabetes. It has many benefits.
Metformin has been used for decades, so its safety profile is known. It's now generic, so it's cheap. It reduces the liver's overproduction of glucose, which is a big problem in people with type 2 diabetes, and also reduces insulin resistance (IR). There are even reports that it is associated with lower rates of certain types of cancer.
Like all drugs, it does have some side effects, primarily nausea in some patients. Some say they can avoid the nausea by eating yogurt or taking the supplement silymarin . I don't know, because the drug never caused me to have nausea.
A more serious side effect is lactic acidosis, which can be fatal. However, that side effect is rare. But metformin users should be aware of its possibility, which increases when the kidneys are not operating fully, which is one reason you should stop taking the drug if you have a procedure like MRI that requires a contrast agent, which can sometimes affect the kidneys, or if your kidney function is impaired for some other reason.
Metformin also mimics, to some extent, the effects of exercise. Both increase insulin sensitivity (reduce IR).
Hence some researchers wondered if the combination of both metformin and exercise would give a better result than either one alone.
To their surprise, they found that it didn't.
Exercise increased insulin sensitivity by 54%. Metformin is known to increase insulin sensitivity from 10 to 30%, although the increase is not seen in all studies. But in this study, when the subjects on metformin exercised, they saw no increase in insulin sensitivity.
A recent study showed a similar effect with antioxidants. IR reductions with exercise were prevented in people taking antioxidants.
In fact, when people who took metformin exercised, their livers produced more glucose and lactate (a gluconeogenesis precursor) than they would have without the metformin.
I find this interesting because I take metformin, and my blood glucose often goes up when I exercise.
Caveat: These results were from insulin resistant nondiabetic subjects taking metformin short term (2 to 3 weeks). They don't yet know what will happen in subjects taking the drug for longer periods.
Do these preliminary results suggest that you should stop taking metformin? Do they suggest that if you take metformin you should stop exercising?
No. Metformin has many benefits at a low cost. And exercise does more than decrease IR: it keeps your heart in good condition and, by building muscle, indirectly increases the amount of glucose your muscles can take up.
Overall, it's a pretty good drug.