gtt is a tiny Sig abbreviation with a big job: it tells the patient how many drops to use in the eye or ear. If you can read it confidently, you prevent a lot of confusion at the counter.
What gtt Drop Dosing Means in a Sig
gtt comes from the Latin guttae and is the standard pharmacy abbreviation for drop(s). In an eye or ear prescription, it is paired with a number, route, and frequency—for example, 1 gtt OU BID means one drop in both eyes twice daily. It describes a counted dose, not a volume like milliliters or teaspoons.
Why gtt Drop Dosing Matters for Pharmacy Technicians
You will see gtt constantly in ophthalmic and otic Sigs, and PTCB expects you to interpret prescription instructions accurately. Technicians must recognize eye routes (OD, OS, OU) versus ear routes (AD, AS, AU), verify the number of drops, and flag unclear or unsafe directions to the pharmacist. Correct data entry and label reading protect patients from wrong-route or wrong-frequency errors.
Practical gtt Dosing Example
Consider Ciprodex otic suspension — 4 gtt AD BID. That is four drops in the right ear twice daily. For an eye example, latanoprost — 1 gtt OU nightly means one drop in each eye at bedtime. You can clarify the Sig and prepare the label, but direct clinical counseling questions to the pharmacist.
Common gtt Mistake and Pro Tip
⚠️ A common mistake is treating gtt as a generic “drop” without confirming the number or route, or confusing OU (both eyes) with AU (both ears). 💡 Pro tip: read the entire Sig aloud as number + route + frequency, then double-check the dosage form matches the route before you finalize entry.
Quick Reference
- gtt = drop(s), not mL or teaspoon
- OD/OS/OU = right eye/left eye/both eyes
- AD/AS/AU = right ear/left ear/both ears
- 1 gtt OU BID = one drop in both eyes twice daily
- If route or count is unclear, ask the pharmacist
Related Concepts
Review Sig codes, route abbreviations, and ophthalmic and otic dosage forms together—they are closely connected on the PTCB exam and in daily practice.