Taking metformin after stopping for a few days is usually no longer effective. After taking metformin generally in about 1 hour can start to take effect, different dosage forms of sugar-lowering effect time may have some differences, for example, taking metformin extended-release tablets effect lasts longer, can reach 12 to 24 hours. If you stop taking metformin a few days after the drug is generally no longer effective, at this time the body’s metformin is basically cleared. It should be noted that, after taking metformin may appear nausea, vomiting, diarrhea, loss of appetite, fatigue and other adverse reactions, if there is no obvious adverse reaction after taking the drug is not recommended to stop taking the drug on their own, the need to stop the patient should be discontinued under the guidance of a doctor.