The concentration of methemoglobin to cause cyanosis-
For Cyanosis to occur,
Sulfhemoglobin should be equal or more than 0.5gm/dL
Methemoglobin should be equal or more than 1.5gm/dL
Deoxygenated hemoglobin should be equal or more than 5gm/dL
5 gm/dl
2 gm/dl
1.5 gm/dl
12 gm/dl