gtt (Drops): What It Means in Nursing Dosage Calculation
Shows the work. Every example is computed with the formula and numbered steps. For study and exam practice, not for patient care.
gtt: The abbreviation for drop, from the Latin gutta (plural gtts). A gravity IV's drip rate is written in gtt/min.
gtt stands for the Latin gutta, a drop; gtts is the plural. In dosage calculation you meet it in two places:
- gtt/mL, the drop factor of IV tubing: how many drops make one milliliter.
- gtt/min, the drip rate of a gravity infusion: how many drops fall in the drip chamber each minute.
A pump is programmed in mL/hr; a gravity infusion is regulated by counting drops. The formula joins the two:
gtt/min = volume (mL) × drop factor (gtt/mL) ÷ time (minutes)
A drop can’t be split, so a drip rate is rounded to a whole number of drops per minute.
Order: 0.45% sodium chloride 500 mL IV over 1 hour. The IV tubing has a drop factor of 10 gtt/mL.
- Volume
- 500 mL
- Infusion time
- 60 minutes
- Drop factor
- 10 gtt/mL
Formula gtt/min = volume × drop factor ÷ minutes.
- gtt/min = volume × drop factor ÷ minutes.
- 500 mL × 10 gtt/mL ÷ 60 minutes = 83.33 gtt/min.
- A drop cannot be split, so round to a whole number: 83 gtt/min.
Answer 83 gtt/min
For any other volume, time, or tubing, use the IV drip rate calculator or the drop factor chart.
Sources
- Clinical Calculations: With Applications to General and Specialty Areas — Elsevier (Kee, Marshall, et al.)
- Calculate with Confidence — Elsevier (Morris)