Calculating Volume

Step 1

Identify the dosage of the drug that you will need, e.g., 40 mg, 3 g, 300 mcg, 20 mEq

Step 2

Locate the drug vial and identify the concentration of the drug, e.g., 20 mg/20 mL, 40 mEq/20 mL, 1000 mcg/2 mL, etc.

Reduce the concentration to X mg/1 mL, so 20 mg/20 mL would be 1 mg/1 mL, 40 mEq/20 mL would be 2 mEq/1 mL.

Step 3

Take the dosage you need and divide it by the ‘X’ you found by reducing the concentration, e.g., 40 mg/1 mg, 10 mEq/2 mEq, 500 mcg/mL, etc.

Step 4

The answer to that is the volume of the drug you need for the dose, e.g., 40 mg/1 mg=40, you’ll need 40 mL of this concentration to get 40 mg, 10 mEq/2 mEq=5, you’ll need 5 mL of this concentration to get 10 mEq, etc
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