Metformin is a fundamental medication for diabetes. Taking it correctly can yield twice the result with half the effort, while taking it incorrectly can lead to significant gastrointestinal side effects.

Last week, a patient came to the clinic. As soon as he entered, he had an air of looking down on everyone. He was around 60 years old and was brought by his children. Perhaps seeing that I was relatively young, he asked if there was an experienced traditional Chinese medicine doctor to help regulate his blood sugar. Clearly, he didn’t think much of me, assuming I was young and inexperienced. Out of respect, I asked him, "Uncle, what seems to be the problem? Let me take a look." He said it was nothing serious, just some diarrhea—no spoiled food or catching a cold. He has diabetes and would experience diarrhea every afternoon after taking metformin at noon, but it would stop once he skipped the dose. He had just been discharged from the hospital recently and took out his discharge record from his pocket to show me. He had been hospitalized at a top-tier hospital in Jinan. I reviewed the final medication orders, and most of them were acceptable, but there was one issue: the patient had been prescribed metformin extended-release tablets, with the instruction to take one tablet in the morning, at noon, and in the evening. I asked the patient, "How do you take metformin?" He replied, "Didn’t you see? As the doctor instructed, three times a day, one tablet each time. I’m taking it correctly." I told him, "You’re taking it wrong. Even the hospital’s prescription for metformin extended-release tablets is unreasonable." The old man immediately widened his eyes and raised his voice, saying, "That’s impossible! The doctor who treated me is a professor from a top-tier hospital. How could this be wrong?" He was convinced he was taking it correctly.

I said, "Don’t get upset. Listen to me: Metformin comes in three formulations—extended-release tablets, regular tablets, and enteric-coated tablets. You’re taking the extended-release tablets. So, what does 'extended-release' mean? Simply put, it has a long half-life, lasting 8 to 12 hours, and the medication is released slowly. Therefore, taking metformin extended-release tablets once in the morning and once in the evening is sufficient. Taking a tablet at noon is unnecessary and only adds to your gastrointestinal burden. If you were taking regular metformin tablets, you would need to take one in the morning, at noon, and in the evening because its half-life is short, usually around 4 hours."

"Think about it, doesn’t that make sense?"

The old man sat there for a moment, muttering to himself, "It shouldn’t be like this. I saw an expert." I said, "Uncle, if you stop taking the metformin extended-release tablet at noon, your diarrhea will improve significantly, and your blood sugar won’t spike." He left somewhat skeptically. Today, he came back to my clinic on his own. This time, he didn’t have the condescending attitude from before. Instead, he looked apologetic and sat in front of me, saying, "Dr. Wu, I’m sorry for my attitude last time. In my mind, older doctors are more experienced. At first, seeing how young you are, I thought you wouldn’t be able to help me. But after following your advice and stopping the noon dose of metformin extended-release tablets, I haven’t had diarrhea since, and my blood sugar has been stable. Thank you for correcting me in time. If I hadn’t met you, I wouldn’t have realized how unreasonable my medication regimen was. Even top-tier hospitals aren’t always reliable."

To the friends with diabetes reading this article, did you understand the point of the story I just shared? Some of you might also be taking metformin incorrectly. Make sure to correct it as soon as possible.