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What Does IU Mean in Medical Terms?
IU stands for international unit. Standard measure of substance activity, error-prone in writing.
international unit
Standard measure of substance activity, error-prone in writing.
⚠ Caution — error-prone abbreviation. IU is on recognised error-prone abbreviation lists (ISMP pattern) because it can be misread or confused with similar terms. Many hospitals restrict or ban it in handwritten orders. Write the full form instead, and always verify against your institution’s approved list.
Where you will see IU
You will most often see IU in medication orders and prescriptions, laboratory orders and test results.
Example
A medication order might be written with “IU” as shorthand for international unit.
Related abbreviations
- 1,25-(OH)2 vitamin D — 1,25-dihydroxyvitamin D
- 14-3-3 — 14-3-3 protein (CSF)
- 17-OHP — 17-hydroxyprogesterone
- 1h GTT — one-hour glucose challenge test
- 21-hydroxylase — 21-hydroxylase deficiency (CAH)
- 25-OH vitamin D — 25-hydroxyvitamin D
- 3% saline — three percent saline (hypertonic)
- 3h GTT — three-hour glucose tolerance test
Browse the full Medical Abbreviations guide — 5,715 entries, searchable A–Z and by specialty.
Educational reference only. This guide is for learning and quick reference. Abbreviations vary between hospitals, countries and specialties, and some are discouraged because they can be misread. Always write and interpret orders using your own institution’s approved abbreviation list, and check anything unclear with the prescriber or your local policy.