Leptin levels: normal range, body fat and resistance

Leptin is a hormone made by your fat cells, so the amount in your blood mostly reflects how much body fat you carry. Your brain reads it as a fuel gauge. More fat means more leptin; a fast or a diet drops it within a day or two, and hunger rises.¹²³

The short version

• Normal depends on your sex and your body fat. Labcorp prints its range by body mass index (BMI): at a BMI of 25 it's 1.1–9.6 ng/mL for men and 5.1–28.0 ng/mL for women. ARUP prints one adult range: 0.5–12.5 for men and 0.5–15.2 for women.⁴⁵
• High usually means more body fat. In a 1996 study of 275 adults, leptin tracked body-fat percentage closely (r = 0.85).¹ "Leptin resistance" is a real research idea, but there's no clinical test for it, so a high level mostly just says "more fat".⁶
• Leptin matters most in two rare conditions. An undetectable level with severe obesity from infancy points to congenital leptin deficiency. A very low level with almost no body fat, very high triglycerides and hard-to-control diabetes fits generalized lipodystrophy, where leptin helps choose treatment.⁷⁸ No leptin number is an emergency by itself.
• It moves fast. A 52-hour fast cut leptin by 64–72%, long before body fat changed much.³ Test in your usual routine, and compare results from the same lab.

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What leptin is

Leptin is a hormone that fat cells release roughly in proportion to their size: as fat builds up in the cells, they make more of it.² When researchers measured leptin leaving fat tissue directly, whole-body production tracked body-fat percentage almost perfectly (rs = 0.93).⁹ Small amounts also come from the stomach and, in pregnancy, the placenta.⁴

Leptin travels to the hypothalamus, the part of the brain that runs hunger and energy use, and locks onto the leptin receptor there.² Plenty of leptin reads as "stores are full": appetite eases and energy use rises.⁴ Falling leptin reads as "starvation". Its clearest effects show up when it's low: replacing leptin reverses those changes in people born without it, in people with almost no fat tissue, and in people whose leptin fell because they lost fat.¹³ In women whose periods stopped from hard training or low weight, leptin injections restored the brain's signals to the ovaries.¹¹

Leptin is a separate test, outside the standard metabolic panel. Labcorp (test 146712) and ARUP (test 0070263) both run it, and some longevity testing companies include it in their panels.⁴⁵¹⁴

What's a normal leptin level?

Start with the range printed on your report, and check how it was built. Labs set leptin ranges in two very different ways:⁴⁵

• Labcorp prints a table by sex and BMI. For adults, the range at a BMI of 20 is 0.4–3.2 ng/mL for men and 2.4–13.4 for women. At a BMI of 30 it's 3.2–28.9 for men and 10.6–58.3 for women.⁴
• ARUP prints one adult range per sex: 0.5–12.5 ng/mL for men and 0.5–15.2 for women, whatever your BMI. It sets no range under age 18.⁵

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That's why the same number can land differently. A woman with a BMI of 30 and a leptin of 30 ng/mL is in range on Labcorp's table (10.6–58.3) and high on ARUP's (0.5–15.2).⁴⁵

Women run about 3 times higher than men. In 204 adults, the average was 17.1 ng/mL in women and 5.8 in men.¹⁵ The gap persists at the same fat mass: premenopausal women are highest, then postmenopausal women, then men, and male hormones (androgens) seem to hold leptin down.¹⁶ Labcorp's table shows it too: at a BMI of 25, the women's range tops out at 28.0 and the men's at 9.6.⁴

Other things shift the normal level:

• Age: leptin was 53% lower in people over 60 in one study of 204 adults.¹⁵
• Pregnancy: the placenta makes leptin, and levels in the second and third trimesters are about twice non-pregnant levels.⁴
• Time of day: highest from midnight to early morning, lowest around noon to midafternoon.¹⁷

"Optimal" leptin: why there's no target number

Most markers have a ladder of "optimal" targets, from longevity clinics down to the lab's range. Leptin has none worth ranking, because the number mostly restates your body fat. The Libby app shows your leptin on your lab's printed range; its marker catalog has no optimal band for this test. Even Superpower, a testing company that sells a leptin test, says on its leptin page that "there is no single ideal value."¹⁴

What research and guidelines do offer is a ladder of what a level can mean, lowest to highest:

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Why there's no low target to aim for:

• Heart disease. In a study nested in 5,661 British men, those in the top third of leptin had 1.25 times the odds of heart disease of those in the bottom third. After accounting for BMI, it was 0.98: no difference. Pooling 7 studies gave 1.44, with a confidence interval that crossed 1.¹⁹
• Weight loss. In a trial of 127 adults given leptin injections or a placebo, starting leptin had no relation to how much weight people lost (P = .88 at 4 weeks, .76 at 24 weeks).²⁰
• Everything else. In 204 adults, body fat, sex and age explained most of the variation in leptin, and leptin had no independent link to blood lipids, insulin, diet or fitness.¹⁵

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So read leptin as a body-fat readout, adjusted for sex. The evidence supports it in the rare conditions below; it gives little support for using leptin to steer routine weight or metabolic decisions. Your weight, waist, fasting insulin, triglycerides and HbA1c answer those questions more directly. Lower is also no prize: in women whose periods stopped from hard training or low weight, leptin was low, and giving it back restored ovulation in 3 of 8.¹¹

What a high leptin usually means

Read it against a range for your sex and BMI first. High for a one-size range can be ordinary for your body.⁴⁵

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The usual reasons, most common first:

• More body fat. By far the most common. In a 1996 study of 275 adults, people with obesity averaged 31.3 ng/mL and normal-weight people 7.5.¹ Leptin follows the actual amount of fat better than BMI does, so a person with more fat than their BMI suggests runs higher.¹⁶
• A range built for the other sex. At the same fat mass, women run higher than men.¹⁶
• Pregnancy. About twice non-pregnant levels in the second and third trimesters.⁴
• Kidney failure. Healthy kidneys clear about 12% of the leptin that passes through them. In 36 people on dialysis, leptin (adjusted for BMI) was more than 4 times that of healthy controls.²²

"Leptin resistance": the idea and the evidence

If leptin curbs appetite, why do people with obesity, who have plenty of it, stay hungry? Researchers call this leptin resistance: a brain that responds less to leptin. Labcorp's own test page calls insensitivity to leptin "a hallmark of most cases of human obesity."⁴ The idea is reasonable. Using a blood level to diagnose it is where the evidence runs thin:

• A 2019 review states that "there are currently no methods for effectively assessing leptin sensitivity in a clinical setting". Studies simply treat a high level as the marker.⁶
• Leading obesity researchers point out that in animal studies, calling an obese animal "leptin resistant" is "synonymous with calling them 'obese,' and adds little". They argue that in diet-driven obesity, the resistance is more a result of weight gain than its main cause.¹³
• In people with a broken leptin receptor, the purest form of leptin resistance, leptin was only as high as their body fat predicted. The authors ruled out the blood level as a marker for the condition.²³
• In the injection trial above, a high starting leptin predicted nothing about who lost weight.²⁰

So a high leptin that fits your body fat says "more fat". Whether your brain hears it normally is a question no blood test answers yet.

What a low leptin usually means

The usual reasons, most common first:

• Low body fat. Lean people run low, because leptin tracks fat.¹
• Fasting, dieting or short sleep. A 52-hour fast cut leptin by 64–72%, 10 days at 1,000 calories a day by 26%, and two nights of restricted sleep by 18%.³¹⁵²¹
• An energy deficit with lost periods. In women whose periods stopped from strenuous exercise or low weight (hypothalamic amenorrhea), leptin was low.¹¹

Rare: generalized lipodystrophy. A near-total lack of body fat, present from birth (congenital) or developing later (acquired). The congenital form affects an estimated 1 in 10 million people.²⁴ With little fat tissue, leptin is low, fat spills into the liver and muscles, and people develop insulin resistance, very high triglycerides and diabetes.⁸ Leptin supports the picture but settles nothing on its own: the 2016 multi-society guideline says there are "no defined serum leptin levels that establish or rule out the diagnosis", because assays are unstandardized and levels overlap the general population. Leptin helps with the choice of treatment.⁸

Very rare: congenital leptin deficiency. Only a few dozen cases have been reported. Babies are born at a normal weight, then are constantly hungry and gain weight fast from the first months of life; puberty is delayed or never comes.² Leptin is very low or undetectable despite a lot of body fat.²⁵ The Endocrine Society calls an undetectable leptin in severe obesity "highly suggestive" of the condition, and suggests genetic testing for extreme obesity before age 5 with extreme hunger.⁷ In three children treated with daily leptin injections for up to 4 years, hunger, fat mass, high insulin and high blood lipids all improved.¹² The guideline notes that recombinant leptin for this condition is available "on a named patient basis through selected centers."⁷

See a clinician promptly if a young child has constant, extreme hunger and fast weight gain from infancy,⁷ or if you're losing body fat without trying and have very high triglycerides or diabetes that's hard to control.⁸ Get urgent care for severe belly pain with very high triglycerides: in lipodystrophy, that combination can be pancreatitis.⁸

Leptin reads best next to its neighbors

On its own, leptin mostly repeats your body fat. Read next to fasting insulin, triglycerides, HDL cholesterol and LH (a pituitary hormone that drives the ovaries and testes), it sorts into four patterns; the table splits the energy-deficit one in two. Our guides to triglycerides, HDL and LH cover each one.

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How fast leptin changes

Leptin clears fast and responds to food within hours. Its half-life in the blood is about 25 minutes (24.9 in one study), so the level follows production closely.⁹

• Fasting: leptin starts to fall after about 12 hours, is lowest at 36 hours, and is back to baseline 24 hours after normal eating resumes.¹⁰
• A longer fast: after 52 hours, leptin fell from 11 to 4 ng/mL in normal-weight adults and from 31 to 12 in adults with obesity.³
• Dieting and sleep: 10 days at 1,000 calories a day lowered it 26%;¹⁵ two nights of restricted sleep lowered it 18%.²¹
• Day and night: it peaks between midnight and early morning, with a 52–76% swing between the night peak and the midday low.¹⁷
• After weight loss: in 50 adults who lost an average of 13.5 kg on a 10-week diet, leptin was still below its starting level a year later, and hunger was still higher.²⁷

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What that means in practice:

• Test in a steady state. A crash diet, a long fast or a run of short nights all pull leptin down, so a result drawn then says more about that week than about your body fat.³²¹
• Trends are steady when life is steady. In the British men's study, a person's leptin correlated 0.79 with their own level 4 years later.¹⁹
• Stay with one lab. Assays are unstandardized, and labs build their ranges differently.⁸⁴⁵

Going deeper: leptin beyond appetite

Puberty and fertility. Children born without leptin have low gonadotropins (hypogonadotropic hypogonadism) and delayed puberty; leptin therapy let puberty start on time.¹²² In women with hypothalamic amenorrhea, leptin raised LH pulses within two weeks and restored ovulation in 3 of 8.¹¹

Thyroid and immune system. In the same children, leptin raised free thyroxine, and it restored CD4 T cells, which were low without it.¹²

Why obesity raises leptin. Fat tissue makes more leptin per gram as it expands, and there's more of it. Clearance stays about the same across body sizes.⁹ The kidneys do part of that clearing, which helps explain why leptin builds up in kidney failure.²²

When the level misleads. Two rare genetic causes of severe early obesity hide behind an ordinary-looking leptin. In children with a broken leptin receptor (3% of 300 people with severe early-onset obesity in one study), leptin was about what their fat mass predicted.²³ Rarer still, some gene changes make leptin that shows up on the test but does nothing. That's why the Endocrine Society points to genetic testing, rather than leptin alone, for a child with extreme early hunger and weight gain.⁷

Questions worth asking

• Which range did my lab use: one based on my sex and BMI, or a single adult range?
• Does my leptin fit my body fat, or is it out of line with my BMI?
• Was I fasting, dieting, short on sleep or pregnant when the blood was drawn?
• What do my fasting insulin, triglycerides and HDL show next to it?
• If my periods have stopped, could too little energy for my training be the reason?
• Is there any reason to think about a rare cause, like lipodystrophy or a genetic form of obesity?

FAQ

What is a normal leptin level? It depends on your sex and body fat. Labcorp's adult range at a BMI of 25 is 1.1–9.6 ng/mL for men and 5.1–28.0 for women; ARUP's adult range is 0.5–12.5 for men and 0.5–15.2 for women.⁴⁵

Why is my leptin high? Most often because of more body fat. Leptin also runs higher in women, in pregnancy and in kidney failure.¹¹⁶⁴²²

Can a leptin test diagnose leptin resistance? No. A 2019 review found "no methods for effectively assessing leptin sensitivity in a clinical setting", and a high level mostly reflects body fat.⁶¹

Does fasting change leptin? Yes, quickly. A 52-hour fast cut it by 64–72%, and it returns to baseline about a day after normal eating resumes.³¹⁰

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This guide is for education, not diagnosis. A clinician who knows your history is the right person to interpret your result.

Footnotes

1. Considine RV, Sinha MK, Heiman ML, et al. Serum immunoreactive-leptin concentrations in normal-weight and obese humans. N Engl J Med. 1996;334(5):292–295. 136 normal-weight and 139 obese adults: averages of 7.5 and 31.3 ng/mL; correlation with body-fat percentage r = 0.85. PubMed ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

2. National Library of Medicine. Congenital leptin deficiency. MedlinePlus Genetics. How fat cells release leptin, the hypothalamus, and the condition's features and rarity. MedlinePlus ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

3. Boden G, Chen X, Mozzoli M, Ryan I. Effect of fasting on serum leptin in normal human subjects. J Clin Endocrinol Metab. 1996;81(9):3419–3423. A 52-hour fast lowered leptin 64% (normal weight) and 72% (obesity), with insulin falling from 16 to 10 µU/mL. PubMed ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

4. Labcorp. Leptin, Serum or Plasma (test 146712). Test page opened September 2026. Adult reference ranges by sex and BMI (from Blum and Juul, 1997), pregnancy levels, and sources of leptin. A commercial reference lab; its ranges are one lab's. labcorp.com ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹

5. ARUP Laboratories. Leptin, Quantitative by Chemiluminescent Immunoassay (test 0070263). Test page opened September 2026. Adult reference intervals: men 0.5–12.5 ng/mL, women 0.5–15.2 ng/mL; none set under 18. A commercial reference lab; its ranges are one lab's. aruplab.com ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

6. Gruzdeva O, Borodkina D, Uchasova E, Dyleva Y, Barbarash O. Leptin resistance: underlying mechanisms and diagnosis. Diabetes Metab Syndr Obes. 2019;12:191–198. PMC ↩ ↩² ↩³

7. Styne DM, Arslanian SA, Connor EL, et al. Pediatric Obesity—Assessment, Treatment, and Prevention: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2017;102(3):709–757. The guideline's genetic-testing advice and its notes on leptin testing. PMC ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹²

8. Brown RJ, Araujo-Vilar D, Cheung PT, et al. The Diagnosis and Management of Lipodystrophy Syndromes: A Multi-Society Practice Guideline. J Clin Endocrinol Metab. 2016;101(12):4500–4511. On leptin testing, the under-4 ng/mL threshold, and the metabolic features of lipodystrophy. PMC ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³

9. Klein S, Coppack SW, Mohamed-Ali V, Landt M. Adipose tissue leptin production and plasma leptin kinetics in humans. Diabetes. 1996;45(7):984–987. Production tracked body fat (rs = 0.93); plasma half-life 24.9 minutes, unrelated to body fat. PubMed ↩ ↩² ↩³ ↩⁴

10. Kolaczynski JW, Considine RV, Ohannesian J, et al. Responses of leptin to short-term fasting and refeeding in humans: a link with ketogenesis but not ketones themselves. Diabetes. 1996;45(11):1511–1515. The time course: decline from 12 hours, lowest at 36 hours, baseline 24 hours after refeeding. PubMed ↩ ↩² ↩³ ↩⁴

11. Welt CK, Chan JL, Bullen J, et al. Recombinant human leptin in women with hypothalamic amenorrhea. N Engl J Med. 2004;351(10):987–997. Eight women whose periods stopped from strenuous exercise or low weight. PubMed ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

12. Farooqi IS, Matarese G, Lord GM, et al. Beneficial effects of leptin on obesity, T cell hyporesponsiveness, and neuroendocrine/metabolic dysfunction of human congenital leptin deficiency. J Clin Invest. 2002;110(8):1093–1103. Three children treated for up to 4 years. PMC ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

13. Myers MG Jr, Leibel RL, Seeley RJ, Schwartz MW. Obesity and leptin resistance: distinguishing cause from effect. Trends Endocrinol Metab. 2010;21(11):643–651. PMC ↩ ↩²

14. Superpower. Leptin biomarker page. Last updated September 24, 2026. States "there is no single ideal value" for leptin and publishes no numeric target. A commercial source, quoted for what it says about targets. superpower.com ↩ ↩²

15. Ostlund RE Jr, Yang JW, Klein S, Gingerich R. Relation between plasma leptin concentration and body fat, gender, diet, age, and metabolic covariates. J Clin Endocrinol Metab. 1996;81(11):3909–3913. 204 adults: women 17.1 vs men 5.8 ng/mL; 53% lower over age 60; 26% lower after 10 days at 1,000 kcal; no independent link to lipids or insulin. PubMed ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

16. Rosenbaum M, Nicolson M, Hirsch J, et al. Effects of gender, body composition, and menopause on plasma concentrations of leptin. J Clin Endocrinol Metab. 1996;81(9):3424–3427. Leptin tracks absolute fat mass better than BMI and stays higher in women after correcting for body composition. PubMed ↩ ↩² ↩³ ↩⁴ ↩⁵

17. Sinha MK, Ohannesian JP, Heiman ML, et al. Nocturnal rise of leptin in lean, obese, and non-insulin-dependent diabetes mellitus subjects. J Clin Invest. 1996;97(5):1344–1347. PMC ↩ ↩² ↩³

18. U.S. Food and Drug Administration. MYALEPT (metreleptin) for injection, prescribing information, revised 3/2024. Indication, limitations of use, contraindication, boxed warning, REMS, and the approval study's baseline leptin. DailyMed ↩ ↩² ↩³ ↩⁴ ↩⁵

19. Sattar N, Wannamethee G, Sarwar N, et al. Leptin and coronary heart disease: prospective study and systematic review. J Am Coll Cardiol. 2009;53(2):167–175. 550 cases and 1,184 controls from 5,661 British men, plus a meta-analysis of 7 prospective studies. PubMed ↩ ↩² ↩³ ↩⁴

20. Heymsfield SB, Greenberg AS, Fujioka K, et al. Recombinant leptin for weight loss in obese and lean adults: a randomized, controlled, dose-escalation trial. JAMA. 1999;282(16):1568–1575. PubMed ↩ ↩² ↩³

21. Spiegel K, Tasali E, Penev P, Van Cauter E. Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Intern Med. 2004;141(11):846–850. A randomized crossover study in 12 men. PubMed ↩ ↩² ↩³ ↩⁴ ↩⁵

22. Sharma K, Considine RV, Michael B, et al. Plasma leptin is partly cleared by the kidney and is elevated in hemodialysis patients. Kidney Int. 1997;51(6):1980–1985. PubMed ↩ ↩² ↩³ ↩⁴

23. Farooqi IS, Wangensteen T, Collins S, et al. Clinical and molecular genetic spectrum of congenital deficiency of the leptin receptor. N Engl J Med. 2007;356(3):237–247. PMC ↩ ↩²

24. National Library of Medicine. Congenital generalized lipodystrophy. MedlinePlus Genetics. Estimated prevalence 1 in 10 million. MedlinePlus ↩

25. Montague CT, Farooqi IS, Whitehead JP, et al. Congenital leptin deficiency is associated with severe early-onset obesity in humans. Nature. 1997;387(6636):903–908. The first human cases. PubMed ↩ ↩² ↩³

26. National Heart, Lung, and Blood Institute. Metabolic Syndrome. NIH. A large waist, high triglycerides and low HDL are among its criteria; also called insulin resistance syndrome; about 1 in 3 U.S. adults. NHLBI ↩ ↩²

27. Sumithran P, Prendergast LA, Delbridge E, et al. Long-term persistence of hormonal adaptations to weight loss. N Engl J Med. 2011;365(17):1597–1604. PubMed ↩