It is also a blunt instrument. Read the sections below before you draw any conclusion from the number, and use the body fat calculator alongside it.
BMI is a screening measure, not a diagnosis, and it does not distinguish fat from muscle. A provider reads it alongside your labs, your history and your waist measurement.
These are the adult thresholds published by the World Health Organization and used by the CDC. They apply to adults aged 20 and over, and they are screening categories rather than diagnoses.
Can signal undernutrition, bone loss or an underlying condition. Worth investigating rather than ignoring.
The reference range for most adults. Metabolic health still varies widely inside it.
Raised risk of type 2 diabetes and cardiovascular disease, particularly when weight sits around the middle.
The threshold at which medical weight management, including GLP-1 medication, is commonly considered.
Higher risk again. Treatment is usually more intensive and more closely monitored.
Sometimes called severe obesity. Associated with substantially higher risk across most organ systems.
In metric, BMI is your weight in kilograms divided by your height in metres squared. In imperial it is your weight in pounds divided by your height in inches squared, multiplied by 703.
That is the whole calculation. There is no adjustment for age, sex, frame or anything else.
The ratio was devised in the 1830s by Adolphe Quetelet, a Belgian statistician, to describe populations. It was never intended as a measure of individual health.
It became a clinical shorthand in the twentieth century because it is cheap, fast and needs nothing but a set of scales and a tape.
In metric, BMI is your weight in kilograms divided by your height in metres squared. In imperial it is your weight in pounds divided by your height in inches squared, multiplied by 703.
That is the whole calculation. There is no adjustment for age, sex, frame or anything else.
Whatever its limitations, BMI is the number that sets the threshold for most medical weight management. GLP-1 medications such as semaglutide and tirzepatide are generally prescribed at a BMI of 30 or above, or 27 and above when it comes with a related condition such as high blood pressure, type 2 diabetes or high cholesterol.
That is a starting criterion, not a decision. Eligibility is confirmed in consultation, with lab work and a review of your history, and a provider decides whether medication is the right tool at all.
A consultation covers your labs, your hormone panel and your history, and turns a screening number into something you can actually act on.
