Skip to content
Educational information only. Not medical advice. We sell nothing and take no affiliate money.
By /
Peptide hormoneHuman trialsFDA approved

Oxytocin

Oxytocin

Last reviewed October 27, 2026 · 24 sources · Written for general readers · Compare with another compound →

The bottom line

Oxytocin is a natural hormone and an FDA approved hospital drug, Pitocin, used to start or strengthen labor and control bleeding after birth. Early studies suggested a nasal spray could boost trust and social behavior, but those results did not hold up well. Placebo controlled trials of the spray for autism, weight loss and sexual function found no benefit over placebo, and none of these are approved uses.

Where the evidence stands

What it is

Oxytocin is a small peptide hormone made of nine amino acids. The version used in medicine is made in a lab so it is free of vasopressin, a closely related hormone that differs from it in two amino acids.[1]

PubChem and the FDA label list its formula as C43H66N12O12S2.[1][2]

The body makes oxytocin mainly in the hypothalamus, a brain area, and releases it from the pituitary gland during labor, breastfeeding and some kinds of stress. Smaller amounts are made in the uterus, placenta, testes and heart.[3] In the blood it lasts only about 1 to 6 minutes before half of it is gone.[1]

Pitocin is approved for two jobs: starting or strengthening contractions before delivery when there is a medical reason, and causing contractions after birth to control bleeding. The label says it is not approved for elective induction, meaning induction just for convenience.[1]

Online, oxytocin nasal sprays are promoted as a "love hormone" for trust, bonding, mood, weight loss and sex. None of these are approved uses.[1]

Name
Oxytocin (Oxytocin)
Other names
Pitocin
Type
Peptide hormone
Formula
C43H66N12O12S2
Molecular weight
About 1007.2 g/mol

What it does in the body

Oxytocin is a natural hormone made in the hypothalamus and released from the pituitary gland. It works through one receptor, the oxytocin receptor, found in the uterus, breasts, kidneys, brain and other organs.[3]

This is the biology, area by area. A change measured in the body, like a higher blood level, does not always mean a person feels a benefit. The claims check below covers that.

Uterus and childbirth

Well established

Oxytocin binds receptors in the muscle wall of the uterus and makes it contract. The uterus becomes most sensitive in early labor at full term, and a drip into a vein acts almost at once.[1] Given right after birth, it cut the risk of heavy bleeding by about half compared with no drug or placebo in a Cochrane review of thousands of women.[4]

Breasts and milk

Well established

When a baby suckles, the body releases oxytocin, which squeezes milk out of the milk glands, the let down reflex. Mice that cannot make oxytocin cannot release milk to their pups.[3]

Kidneys and water balance

Well established

Oxytocin makes the kidneys hold on to water, much like its cousin vasopressin. With long drips this can cause water intoxication, with seizures and coma in severe cases.[1]

Heart and blood vessels

Well established

In large amounts it can raise blood pressure, and the label lists irregular heartbeats and episodes of high blood pressure in mothers.[1] In rats, oxytocin made by the heart helps the kidneys get rid of salt.[3]

Brain and social behavior

Measured in people

In 11 people given a nasal spray, oxytocin rose in the blood within 15 minutes but in the fluid around the brain only by 75 minutes, and the two levels did not track each other.[5] In 15 men, the spray calmed the amygdala, a fear center, on brain scans.[6] These brain changes have not turned into proven benefits for trust or autism in larger trials.[7][8]

Stress response

Measured in people

In 37 men put through a stressful public speaking test, the spray lowered anxiety. The lowest levels of cortisol, the main stress hormone, came when oxytocin was combined with support from a best friend.[9]

Appetite and fat

Measured in people

In 61 adults with obesity, eight weeks of a nasal spray cut calories eaten at one test meal by about 150, but weight, body fat and liver fat did not change.[10]

How it works

Oxytocin acts on the body and the brain.[1][11]

  • In the womb, it makes the uterine muscle contract.[1]
  • It also makes the kidneys hold on to water, which is why long infusions can cause dangerous water buildup.[1]
  • In breastfeeding, it triggers milk release.[3]
  • In the brain of some rodents, oxytocin and vasopressin help animals recognize each other and form pair bonds.[11]

The effects on the uterus are certain. How much a nasal spray reaches the human brain and changes behavior is still debated.

What the research shows

We keep animal and human evidence apart. A result in animals is a reason to study something in people, not proof that it works in people.

Animal and lab studies

Strong animal evidence for bonding and milk release

  • Studies in monogamous voles showed that oxytocin and vasopressin, working with the brain's dopamine reward system, help form partner bonds after mating.[11]
  • Differences in where these hormone receptors sit in the brain may explain why some species pair bond and others do not.[11]
  • Mice bred without oxytocin cannot release milk to their pups, which shows its key role in breastfeeding.[3]
  • In rats, oxytocin made in the heart works with another heart hormone to make the kidneys get rid of salt and potassium.[3]

Limit: Vole bonding biology does not prove that a nasal spray changes human relationships or social skills.

Human studies

Proven for labor, weak or negative for everything else

  • Labor and bleeding: oxytocin's hospital uses, given by drip into a vein or shot into a muscle, are long established and FDA approved.[1]
  • Preventing heavy bleeding: a 2019 Cochrane review found that a shot of oxytocin right after birth roughly halved the risk of heavy bleeding compared with no drug or placebo (6 trials, 4,162 women), though the evidence was rated low certainty.[4]
  • Oxytocin versus carbetocin: in a double blind trial of 29,645 women in 10 countries, a shot of oxytocin after vaginal birth and a heat stable related drug worked about the same, with heavy bleeding or need for more drugs in about 14% of each group. Side effects did not differ.[22]
  • Does the spray reach the brain: in a study of 15 people, 11 given a nasal spray and 4 given placebo, the spray raised oxytocin in the blood within 15 minutes and in the fluid around the brain by 75 minutes.[5]
  • Brain scans: in a crossover study of 15 healthy men, the spray reduced activity in the amygdala, a fear center, while viewing frightening images.[6]
  • Stress: in 37 healthy men given a stressful speech test, the spray reduced anxiety, and cortisol was lowest when it was paired with a friend's support.[9]
  • Trust: a widely cited 2005 study found people given oxytocin nasal spray trusted strangers more in a money game. A 2015 critical review concluded that this effect has not replicated well.[12][13] A large, double blind replication planned and peer reviewed before it was run found no effect on trust.[7]
  • Autism in children: a large, placebo controlled trial in 290 children and teens found no improvement in social behavior after 24 weeks of nasal oxytocin compared with placebo.[14][15]
  • Autism in adults: in a crossover trial of 109 men with autism at seven Japanese hospitals, a newer nasal spray given in four week periods did not clearly improve social reciprocity in the main analysis, and no other outcome beat placebo.[16]
  • Autism overall: a 2025 analysis pooling 12 randomized trials with 498 people found no overall effect on social problems or repetitive behaviors. Benefit appeared only at the highest amounts tested, which the authors say needs more study.[8]
  • Obesity: a 2024 double blind trial gave 61 adults with obesity a nasal spray or placebo several times a day for eight weeks. Weight barely moved in either group, and body fat, belly fat, liver fat and energy use did not improve. Calories eaten at one test meal were about 150 lower with oxytocin. Side effects did not differ from placebo, and none were serious.[10]
  • Obesity after brain tumors: in a pilot crossover trial of 13 young people with hypothalamic obesity, eight weeks of spray at mealtimes did not clearly change weight. Nosebleeds, nasal irritation, headache and nausea were about as common with placebo.[17]
  • Prader Willi syndrome: a 2023 analysis pooled 3 trials with about 92 people for hunger and 3 with about 94 for weight. The spray did not reduce hunger or weight compared with placebo, though some behavior scores improved.[18]
  • Sexual problems in women: in a 22 week crossover trial of 30 women, oxytocin spray before sex and placebo improved sexual function and mood about equally.[19] In 27 healthy women, a single spray did not change arousal, orgasm or blood flow in the lab.[20]
  • Addiction: in 48 men in group therapy for methamphetamine use, oxytocin spray improved attendance and slightly improved group closeness, but drug use, craving and anxiety did not change. No serious side effects occurred.[21]

Limit: Many early nasal spray studies were small and tested a single spray. The larger, longer, placebo controlled trials have mostly come back negative.

Claims check

The most common claims about this compound, and what studies actually found. Verdicts rate the evidence, not whether you should use it.

Starts labor and stops bleeding after birth

Shown in people

Given by drip or shot in the hospital, oxytocin is FDA approved to start or strengthen contractions for medical reasons and to control bleeding after delivery.[1] In a Cochrane review, a shot after birth roughly halved the risk of heavy bleeding versus no drug or placebo in over 4,000 women.[4]

Builds trust and bonding

Mixed results

A widely cited 2005 study found people given the nasal spray trusted strangers more in a money game.[12] A 2015 critical review found this effect has not replicated well, and a large 2020 replication planned in advance found no effect on trust.[13][7] Bonding effects are best shown in voles.[11]

Improves social skills in autism

No benefit in trials so far

In a placebo controlled trial of 290 children and teens with autism, 24 weeks of nasal oxytocin did not improve social behavior more than placebo.[14][15] In 109 men with autism in Japan, a newer nasal spray did not clearly improve social reciprocity over placebo in the main analysis.[16] A 2025 analysis of 12 trials with 498 people found no overall effect on social problems.[8]

Helps you lose weight and curbs appetite

No benefit in trials so far

In a double blind trial of 61 adults with obesity, eight weeks of nasal oxytocin left weight almost unchanged, the same as placebo, with no change in body fat or liver fat, though people ate about 150 fewer calories at one test meal.[10] A pilot crossover trial in 13 young people with obesity from brain tumors found no clear weight change.[17] A 2023 analysis of trials in Prader Willi syndrome, a genetic condition with extreme hunger, found no effect on hunger or weight.[18]

Boosts libido and orgasm

No benefit in trials so far

In a 22 week crossover trial of 30 women with sexual problems, sexual function scores rose 26% with oxytocin spray and 31% with placebo, with no real difference.[19] In 27 healthy women tested in a lab, the spray did not change arousal, orgasm or genital blood flow.[20]

Lowers stress and anxiety

Mixed results

In 37 men facing a stressful speech test, one spray lowered anxiety, and cortisol was lowest when the spray was combined with a supportive friend.[9] In 15 men, it calmed fear responses in the amygdala on brain scans.[6] These were small lab studies of one spray, and the addiction trial below found no drop in anxiety over weeks.[21]

Helps with addiction and cravings

No benefit in trials so far

In a randomized trial of 48 men with methamphetamine addiction, oxytocin spray before group therapy improved attendance, but did not reduce craving, anxiety or drug use compared with placebo.[21]

Known risks and side effects

  • Uterine overstimulation. Too strong a response in labor can cause very tight or nonstop contractions, uterine rupture, fetal distress or fetal death. That is why it is given in a hospital with monitoring.[1]
  • Water intoxication. Its water holding effect can cause water intoxication with long infusions. Severe cases with seizures, coma and maternal death have been reported.[1]
  • Heart rhythm, blood pressure and allergy. The label lists irregular heartbeats, episodes of high blood pressure, bleeding in the brain, nausea, vomiting and serious allergic reactions, including anaphylaxis, in mothers. Babies can have slow heart rate and other rhythm problems.[1]
  • Spray side effects. Spray trials reported nosebleeds, nasal irritation, headache and nausea at rates similar to placebo, and no serious side effects over eight weeks. Some participants in one pilot trial had changes on heart rhythm tracings, though about as often with placebo.[10][17]
  • Unregulated nasal sprays. The Pitocin label covers hospital use for labor and bleeding after birth only. Oxytocin sprays sold online for mood, bonding or weight fall outside any approved use, and their strength, purity and sterility are not checked by FDA.[1]

Regulatory status

Today: Oxytocin is FDA approved as Pitocin for medical induction or strengthening of labor and for bleeding after birth. Use for social behavior, autism, weight, sex or mood is not an approved use.[1] Oxytocin is not named on the 2026 WADA Prohibited List or on the 2027 list that starts January 1, 2027.[23][24]

Sources

  1. Par Health USA. Pitocin (oxytocin) injection prescribing information. DailyMed, U.S. National Library of Medicine. DailyMed
  2. National Center for Biotechnology Information. PubChem Compound Summary for CID 439302, Oxytocin. PubChem CID 439302
  3. Gimpl G, Fahrenholz F. The oxytocin receptor system: structure, function, and regulation. Physiol Rev. 2001;81(2):629-683. PMID 11274341
  4. Salati JA, Leathersich SJ, Williams MJ, Cuthbert A, Tolosa JE. Prophylactic oxytocin for the third stage of labour to prevent postpartum haemorrhage. Cochrane Database Syst Rev. 2019;4(4):CD001808. PMID 31032882
  5. Striepens N, Kendrick KM, Hanking V, Landgraf R, et al. Elevated cerebrospinal fluid and blood concentrations of oxytocin following its intranasal administration in humans. Sci Rep. 2013;3:3440. PMID 24310737
  6. Kirsch P, Esslinger C, Chen Q, Mier D, et al. Oxytocin modulates neural circuitry for social cognition and fear in humans. J Neurosci. 2005;25(49):11489-11493. PMID 16339042
  7. Declerck CH, Boone C, Pauwels L, Vogt B, Fehr E. A registered replication study on oxytocin and trust. Nat Hum Behav. 2020;4(6):646-655. PMID 32514040
  8. Zhang Y, Zhang X, Huang L. Optimal dose of oxytocin to improve social impairments and repetitive behaviors in autism spectrum disorders: meta-analysis and dose-response meta-analysis of randomized controlled trials. Front Psychiatry. 2025;15:1477076. PMID 39944132
  9. Heinrichs M, Baumgartner T, Kirschbaum C, Ehlert U. Social support and oxytocin interact to suppress cortisol and subjective responses to psychosocial stress. Biol Psychiatry. 2003;54(12):1389-1398. PMID 14675803
  10. Plessow F, Kerem L, Wronski ML, Asanza E, O'Donoghue ML, Stanford FC, et al. Intranasal Oxytocin for Obesity. NEJM Evid. 2024;3(5):EVIDoa2300349. PMID 38815173
  11. Young LJ, Wang Z. The neurobiology of pair bonding. Nat Neurosci. 2004;7:1048-1054. Nat Neurosci 2004
  12. Kosfeld M, Heinrichs M, Zak PJ, Fischbacher U, Fehr E. Oxytocin increases trust in humans. Nature. 2005;435(7042):673-676. Nature 2005
  13. Nave G, Camerer C, McCullough M. Does Oxytocin Increase Trust in Humans? A Critical Review of Research. Perspect Psychol Sci. 2015;10(6):772-789. Perspect Psychol Sci 2015
  14. Study of Oxytocin in Autism to Improve Reciprocal Social Behaviors (SOARS-B). ClinicalTrials.gov NCT01944046. NCT01944046
  15. Sikich L, Kolevzon A, King BH, McDougle CJ, Sanders KB, Kim SJ, et al. Intranasal Oxytocin in Children and Adolescents with Autism Spectrum Disorder. N Engl J Med. 2021;385(16):1462-1473. PMID 34644471
  16. Yamasue H, Kojima M, Kuwabara H, Kuroda M, Matsumoto K, Kanai C, et al. Effect of a novel nasal oxytocin spray with enhanced bioavailability on autism: a randomized trial. Brain. 2022;145(2):490-499. PMID 35067719
  17. McCormack SE, Wang Z, Wade KL, Dedio A, Cilenti N, Crowley J, et al. A Pilot Randomized Clinical Trial of Intranasal Oxytocin to Promote Weight Loss in Individuals With Hypothalamic Obesity. J Endocr Soc. 2023;7(5):bvad037. PMID 37153702
  18. Shalma NM, Alsharabasy MA, Taha AM, Alsawareah A, et al. The efficacy of intranasal oxytocin in patients with Prader-Willi syndrome: A systematic review and meta-analysis. Diabetes Metab Syndr. 2023;17(2):102711. PMID 36774885
  19. Muin DA, Wolzt M, Marculescu R, Sheikh Rezaei S, Salama M, Fuchs C, et al. Effect of long-term intranasal oxytocin on sexual dysfunction in premenopausal and postmenopausal women: a randomized trial. Fertil Steril. 2015;104(3):715-723.e4. PMID 26151620
  20. Kruger THC, Deiter F, Zhang Y, Jung S, Schippert C, Kahl KG, et al. Effects of Intranasal Oxytocin Administration on Sexual Functions in Healthy Women: A Laboratory Paradigm. J Clin Psychopharmacol. 2018;38(3):239-242. PMID 29596150
  21. Stauffer CS, Moschetto JM, McKernan S, Meinzer N, Chiang C, Rapier R, et al. Oxytocin-enhanced group therapy for methamphetamine use disorder: Randomized controlled trial. J Subst Abuse Treat. 2020;116:108059. PMID 32741502
  22. Widmer M, Piaggio G, Nguyen TMH, Osoti A, et al. Heat-Stable Carbetocin versus Oxytocin to Prevent Hemorrhage after Vaginal Birth. N Engl J Med. 2018;379(8):743-752. PMID 29949473
  23. World Anti-Doping Agency. The 2026 Prohibited List. WADA 2026
  24. World Anti-Doping Agency. The 2027 Prohibited List. In force January 1, 2027. WADA 2027
Medical disclaimer

This page is educational information only. It is not medical advice and does not replace care from a licensed medical provider. Do not use this page to decide whether to take any substance. Talk to a licensed medical provider first.

Found an error or a newer study? We correct pages fast.

Report a correction →
Scroll to Top