An increase in 2,3-DPG shifts the oxyhemoglobin dissociation curve to the:

• A. Left
• B. Right
• C. No shift
• D. Upward

Answer: (B)

An increase in 2,3-DPG lowers hemoglobin’s affinity for oxygen by binding to deoxygenated hemoglobin and stabilizing the low-oxygen (T) form. This causes the oxyhemoglobin dissociation curve to shift to the right, meaning a higher PO2 is needed for the same saturation and the P50 increases. In other words, oxygen is released more readily to tissues, which is beneficial in states of chronic hypoxia or anemia when tissues need more oxygen delivery. A leftward shift would indicate higher affinity (lower P50) and occurs with decreased 2,3-DPG, lower temperature, or alkaline pH. The upward option isn’t used to describe this dissociation curve shift.