Medication safety is paramount. Nurses are the final line of defense against medication administration errors, making dosage calculations an indispensable clinical competency.
The Desired over Have Formula
This is the most common formula used for simple tablet or liquid calculations:
Formula: (Desired Dose / Have Dose) × Quantity = Amount to Administer
Example: The doctor orders Digoxin 0.25 mg PO. The pharmacy supplies Digoxin 0.125 mg tablets. How many tablets should the nurse administer?
- Desired (Order) = 0.25 mg
- Have (Stock) = 0.125 mg
- Quantity (Vehicle) = 1 tablet
- Calculation: (0.25 / 0.125) × 1 = 2 tablets.
IV Flow Rate Calculations
To calculate flow rates in drops per minute (gtts/min):
Formula: (Total Volume in mL × Drip Factor) / Time in Minutes = Flow Rate (gtts/min)
