At what BMI value is a person considered underweight?

A person is considered underweight when their Body Mass Index (BMI) is calculated to be 18.5 or lower. The BMI scale categorizes individuals into various weight categories, and the threshold for underweight is set specifically at a value of 18.5. This classification helps health professionals identify individuals who may be at risk for health issues associated with being underweight, such as nutritional deficiencies, weakened immune function, and other health concerns.

To understand this better, it's important to know that a BMI of 18.5 is the cutoff point; therefore, any BMI that is 18.5 or below clearly falls into the underweight category. In contrast, the other BMI values mentioned are indicative of either a normal weight (up to 24.9), overweight (between 25 and 29.9), or obesity (30 and above). Thus, a BMI of 18.5 or lower specifically addresses those considered underweight as per established health guidelines.