There are three available metformin strengths: 500-mg, 850-mg, and 1000-mg tablets (625-mg and 750-mg tablets were once available but have since been discontinued). A long-acting form of the medication (metformin ER) is also available; it comes in two strengths, 500-mg and 750-mg tablets. Long-acting metformin 1000-mg tablets are also available and are sold under the brand names of Fortamet® and Glumetza®. A liquid version of metformin, called Riomet®, is also available.
For regular metformin, the recommended starting dosage for children ages 10 to 16 is 500 mg twice daily. The usual starting dose for people 17 years old and over is 500 mg twice daily or 850 mg once daily. For the long-acting form, the starting dose is metformin ER 500 mg once daily, and the maximum dose is metformin ER 2000 mg once daily (or metformin ER 1000 mg twice daily).
(Click Metformin Dosing to find out how dosing works for people who also take insulin and for more information on when and how to take this medication.)