Figure 1.

Summary of previously published equations to adjust hemoglobin for altitude and current WHO adjustment values^a.

^aAdjustment is the amount added to the hemoglobin (Hb) cutoff defining anemia or subtracted from an individual’s observed hemoglobin level.

^bBased on the equation Hb_adjustment (g/L) = 6.83 × EXP(0.000445 × altitude) +113.3 and reported as the difference between hemoglobin at a given altitude and hemoglobin at sea level (0 m). Hemoglobin was assessed up to 4540 m.^9,12

^cBased on the equation Hb_adjustment (g/L) = [(−0.032 × (altitude × 0.0032808) + 0.022 ×(altitude × 0.0032808)²) × 10]. Hemoglobin was assessed up to approximately 2150 m.⁸

^dBased on the equation Hb_adjustment (g/L) = 3.44 × EXP(0.000633 × altitude) + 116.9 and reported as the difference between hemoglobin at a given altitude and hemoglobin at sea level (0 m). Hb was assessed up to 3400 m.¹²

^eWHO cutoffs shown with an X at each (altitude, Hb_adjustment) coordinate with the recommended Hb adjustment value shown above each X.⁷