Underweight BMI Screening — WHO Thinness Scale
A clinical screening reference for BMI values below the healthy range, using the WHO's mild/moderate/severe thinness bands. This tool cannot diagnose an eating disorder — see the support resources below if you or someone you know needs help.
Underweight BMI Screening
WHO adult thinness classification
Your BMI
19.1
Normal Range
Within the WHO healthy weight range for adults.
📊 WHO Adult Thinness Categories
Understanding These Categories
📏 A Finer-Grained Scale
Standard BMI stops at one "underweight" label below 18.5. The WHO thinness grades split that further so clinicians can gauge severity, not just presence.
🩺 A Starting Point, Not an Answer
A low BMI reading raises a question worth asking a doctor — it never answers why on its own, and the cause matters more than the number.
🤝 If You're Concerned About Someone
Approach with care rather than a number — a compassionate conversation and encouragement to see a doctor matters far more than any calculator result.
☎️ Need to Talk to Someone Now?
NEDA Helpline (US): call or text 1-800-931-2237. Crisis text line: text "NEDA" to 741741, available 24/7.
— FAQ