Frequently asked questions
What is body surface area used for?
BSA is primarily used in medicine for calculating drug dosages (especially chemotherapy), assessing burn extent, determining cardiac index, and calibrating renal clearance. Many drugs are dosed per m² of BSA because it correlates better with metabolic rate than weight alone.
Which BSA formula is most accurate?
For adults, Mosteller and Du Bois give very similar results and either is acceptable clinically. Du Bois is the historical standard used in most drug dosing tables. Haycock is preferred for children and infants because it was validated on a pediatric population. The difference between formulas is typically less than 3%.
What is a normal body surface area?
Average adult BSA is approximately 1.7 m² for women and 1.9 m² for men. The range for adults is roughly 1.4–2.4 m². Drug dosing tables often use 1.73 m² as the reference 'standard' adult BSA, which is why renal clearance is reported per 1.73 m².
Why not just use body weight for drug dosing?
BSA correlates more closely with metabolic rate, blood volume, and organ size than weight alone. A 100 kg muscular person and a 100 kg obese person have very different metabolic profiles. BSA better captures the functional tissue mass that processes and eliminates drugs.
Can BSA be used for children?
Yes, and it is especially important for pediatric drug dosing. Use the Haycock formula for children and infants, as it was derived from pediatric data. The Mosteller formula also performs well in children. BSA-based dosing is preferred over weight-based dosing for most pediatric chemotherapy.
Does BSA change if I lose or gain weight?
Yes. BSA depends on both height and weight, so significant weight changes alter your BSA. Height changes minimally in adults, but a 10 kg weight change typically shifts BSA by about 0.1 m². If you are on BSA-dosed medication, inform your doctor of major weight changes.