What does gtt mean on a prescription?
gtt means drops, from the Latin guttae. “2 gtt OS BID” means two drops into the left eye twice a day.
- Means:
- drops
- From:
- guttae
- Type:
- What form
- Also written:
- gtt, gtts, GTT
What it means in practice
You will see gtt mostly on eye and ear prescriptions, usually with an abbreviation for which eye or ear. One gtt is one drop — the volume varies slightly by bottle, which is why doses are counted in drops rather than millilitres.
Example on a prescription
Chloramphenicol 0.5% 2 gtt OS QID
Put two drops of chloramphenicol 0.5% into the left eye four times a day.
Commonly confused with
- ODIn eye prescriptions OD means the right eye, so “gtt OD” is about which eye, not how often.
Worth knowing
In laboratory contexts GTT also abbreviates glucose tolerance test, an unrelated meaning. On a prescription for drops, gtt means drops.
Frequently asked questions
What does gtt mean on a prescription?
Drops. The number before it is how many drops per dose.
What does 2 gtt OU mean?
Two drops into both eyes — OU is oculus uterque, each eye.
Related abbreviations
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This page explains prescription notation for general information. It is not medical advice and does not replace your prescriber or pharmacist. If a label is unclear or differs from what you were told, check with your pharmacy before taking the medicine.