A dose of 250 mg of metformin is ordered. On hand are 500 mg tablets. How many tablets should be given?

A dose of 250 mg of metformin is ordered. On hand are 500 mg tablets. How many tablets should be given?

• A. 0.25 tablet
• B. 1 tablet
• C. 0.75 tablet
• D. 0.5 tablet

Answer: (D)

Understanding how to scale a dose to a tablet strength is the key. You divide the amount prescribed by the amount each tablet contains to see how many tablets to give. Here, the prescription is 250 mg and each tablet is 500 mg. 250 mg divided by 500 mg per tablet equals 0.5, so half a tablet is required. This is the standard way to convert a dose to a number of tablets when the tablet strength doesn’t match the exact dose. In practice, check whether the tablet can be safely split (use a scored tablet if splitting) and follow any rounding or formulation guidelines.

Understanding how to scale a dose to a tablet strength is the key. You divide the amount prescribed by the amount each tablet contains to see how many tablets to give. Here, the prescription is 250 mg and each tablet is 500 mg. 250 mg divided by 500 mg per tablet equals 0.5, so half a tablet is required. This is the standard way to convert a dose to a number of tablets when the tablet strength doesn’t match the exact dose. In practice, check whether the tablet can be safely split (use a scored tablet if splitting) and follow any rounding or formulation guidelines.