Leptin
A hormone made by fat tissue that signals energy stores to the brain.
| Typical reference range (male) | 0.3–13.4 ng/mL |
| Typical reference range (female) | 4.7–23.7 ng/mL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
Leptin is secreted mainly by adipose tissue in proportion to fat mass. It acts on the hypothalamus to reduce appetite and increase energy expenditure, and also influences reproductive and thyroid function.
Why it matters
Leptin rises with body fat; very high levels relative to body fat suggest leptin resistance, a state where the brain no longer responds normally, often accompanying obesity and insulin resistance.
What a high result can mean
High levels are typical of obesity, leptin resistance and insulin resistance. Women naturally have higher levels than men at the same body fat.
What a low result can mean
Low levels occur with low body fat, prolonged calorie restriction, intense endurance training and rare congenital leptin deficiency; low leptin can suppress reproductive hormones and thyroid output.
What affects the result
Levels follow a daily rhythm (higher at night) and drop quickly with calorie restriction, before fat is lost. Reference ranges are usually BMI- and sex-specific. Interpret with body composition, insulin and adiponectin.
Units and conversion
Usually reported in ng/mL.
- From ug/L: multiply by 1 to get ng/mL
Also called on lab reports
Leptin, Serum
Related tests: Glucose & Metabolic
This page is educational and does not replace advice from a healthcare professional.