Oxytocin is the rare peptide with a US label, a long research literature and a research-vial market — and each of the three counts it in a different unit. The label uses USP units and milliunits per minute; research on social behaviour uses international units squirted into the nose; and a research vial is labelled in milligrams. Most dosage searches land on hospital infusion tables. This page sets the three side by side and does the conversion. Medibact's oxytocin guide covers the molecule and its evidence.
The conversion that joins the three
The WHO 4th International Standard for oxytocin (NIBSC code 76/575) is an ampoule containing approximately 21 mcg of oxytocin, assigned a potency of 12.5 international units. That fixes the ratio:
| Amount | Micrograms (at 1.68 mcg per IU) |
|---|---|
| 1 IU | 1.68 |
| 10 IU | 16.8 |
| 24 IU | 40.3 |
| 48 IU | 80.6 |
| 2 mg vial | ≈ 1,190 IU |
| 5 mg vial | ≈ 2,980 IU |
The ratio matters most when a vial's milligrams are converted into nasal IU. US labels count in USP units, and the Pitocin label does not state a mass per unit. How the same kind of WHO reference fixes different factors for insulin and growth hormone, and none for hCG, is on why every substance has its own IU factor.
What the US label states
Oxytocin is approved in the US as an injection only, at 10 USP units/mL (Pitocin and several generics in Drugs@FDA). Its label, effective 2026-05-06:
| Use | Dose and route |
|---|---|
| Induction or stimulation of labour | IV infusion only; 10 units in 1,000 mL (10 mU/mL); start 0.5–1 mU/min, increase by 1–2 mU/min every 30–60 min; rates above 9–10 mU/min rarely required at term |
| Postpartum bleeding, IV | 10–40 units added to a running infusion (maximum 40 units per 1,000 mL) |
| Postpartum bleeding, IM | 10 units after delivery of the placenta |
The label's half-life is about 1 to 6 minutes, which is why the obstetric dose is a continuous drip measured per minute and adjusted against the contractions it produces. The label reserves the drug for medical indications and states it is not indicated for elective induction.
The nasal research doses
Intranasal oxytocin is the standard route in behavioural research, and the literature is large: PubMed held 1,322 records with oxytocin and intranasal in the title or abstract on 2026-09-28, 455 of them tagged as randomised trials.
| Setting | Dose | Source |
|---|---|---|
| Healthy adults, social cognition | 1 to 48 IU, most often 24 IU, single doses | Neurosci Biobehav Rev 2025 (PMID 40882784), systematic review |
| Children with autism | target 48 IU a day, 24 weeks | SOARS-B, NEJM 2021 (PMID 34644471), 290 enrolled |
| Schizophrenia | 9 trials; higher doses (> 40–80 IU) suggested a benefit that vanished when one outlier was removed | Int J Neuropsychopharmacol 2021 (PMID 33890987) |
| Mental disorders, pooled | 42 trials, 1,922 people, g = 0.17, not significant | Neurosci Biobehav Rev 2026 (PMID 42134427) |
The review of healthy-adult studies describes the evidence for an "inverted-U" dose response as resting largely on studies that did not compare doses directly. The 2026 meta-analysis found no moderation by dose. The US nasal product, Syntocinon at 40 USP units/mL, is listed as discontinued; at that strength a 24-unit dose is 0.6 mL of spray.
Units per vial size
A research vial is labelled in milligrams, so convert IU to micrograms first, then use units on a U-100 syringe = mcg ÷ mcg/mL × 100. Vial sizes in this site's data are 2 and 5 mg:
| Amount | 2 mg + 4 mL (500 mcg/mL) | 2 mg + 2 mL (1,000 mcg/mL) | 5 mg + 5 mL (1,000 mcg/mL) | 5 mg + 2 mL (2,500 mcg/mL) |
|---|---|---|---|---|
| 10 IU (≈ 16.8 mcg) | 3.4 | 1.7 | 1.7 | 0.7 |
| 24 IU (≈ 40.3 mcg) | 8.1 | 4.0 | 4.0 | 1.6 |
| 48 IU (≈ 80.6 mcg) | 16.1 | 8.1 | 8.1 | 3.2 |
Two cautions follow from the arithmetic. At the concentrated end, a nasal-sized amount is under two syringe marks, where one mark is a large share of the amount. And the syringe arithmetic says nothing about delivery into the nose, which depends on the spray device and the volume it puts out per puff. The mg to mcg page covers the milligram step, the insulin syringe units page the small barrels, and the oxytocin calculator any other vial. The peptide dosage chart sets oxytocin beside the other compounds and the units each is counted in.
What is not established
No regulator has reviewed a nasal oxytocin dose for social, psychiatric or wellbeing use, and the largest trials of repeated nasal dosing were negative. How much of a nasal dose reaches the brain is not settled in the sources opened. A research vial's milligram label says nothing about potency in units unless it has been assayed against a standard, and whether a vial sold as oxytocin contains it, and how much, is not known without an assay. Nothing on this page is a dose or a schedule.
Sources and dates
Opened 2026-09-28: WHO 4th International Standard for oxytocin, NIBSC 76/575 instructions for use (version 4.0, dated 30 April 2013); the Pitocin label through openFDA (effective 2026-05-06; dosage and administration, clinical pharmacology, boxed notice); Drugs@FDA through openFDA (oxytocin applications and their marketing status); PubMed through NCBI E-utilities (oxytocin and intranasal in title or abstract, with the randomised-trial filter) and the abstracts of PMIDs 40882784, 34644471, 33890987 and 42134427. IU-to-microgram, per-vial and unit figures are arithmetic by this site. Corrections go to the contact page.