I don't take them but this website will explain about the dosage.
http://www.medicines.org.uk/emc/medicine/20952/
Treatment of type 2 diabetes mellitus in adults, particularly in overweight patients, when dietary management and exercise alone does not result in adequate glycaemic control. Glucophage SR may be used as monotherapy or in combination with other oral antidiabetic agents, or with insulin.
4.2 Posology and method of administration
Monotherapy and combination with other oral antidiabetic agents:
• The usual starting dose is one tablet of Glucophage SR 500 mg once daily.
• After 10 to 15 days the dose should be adjusted on the basis of blood glucose measurements. A slow increase of dose may improve gastro-intestinal tolerability. The maximum recommended dose is 4 tablets of Glucophage SR 500 mg daily.
• Dosage increases should be made in increments of 500 mg every 10-15 days, up to a maximum of 2000 mg once daily with the evening meal. If glycaemic control is not achieved on Glucophage SR 2000 mg once daily, Glucophage SR 1000 mg twice daily should be considered, with both doses being given with food. If glycaemic control is still not achieved, patients may be switched to standard metformin tablets to a maximum dose of 3000 mg daily.
• In patients already treated with metformin tablets, the starting dose of Glucophage SR should be equivalent to the daily dose of metformin immediate release tablets. In patients treated with metformin at a dose above 2000 mg daily, switching to Glucophage SR is not recommended.
• If transfer from another oral antidiabetic agent is intended: discontinue the other agent and initiate Glucophage SR at the dose indicated above.
• Glucophage SR 750 mg and Glucophage SR 1000 mg are intended for patients who are already treated with metformin tablets (prolonged or immediate release).
• The dose of Glucophage SR 750 mg or Glucophage SR 1000 mg should be equivalent to the daily dose of metformin tablets (prolonged or immediate release), up to a maximum dose of 1500 mg or 2000 mg respectively, given with the evening meal.