Physiology General fcb29e38 Central cyanosis is seen if A Methemoglobin 0.5 gm/dl B O2 saturation < 85% C O2 saturation < 94% D Hb – 4 gm% High-Yield Explanation Oxygen saturation should be less than 85% for central cyanosis to occur. Deoxyhemoglobin level should be at least 5gm%.