1 IU by 1958 WHO 4th International Standard (52% bovine and 48% porcine pancreas purified) = 0.04167 mg insulin. 1 mg insulin = 23.998 IU.
1 IU of 1986 WHO 1st International Standard (human insulin) = 0.03846 mg. 1 mg = 26 IU.
The molecular weight of insulin is 5,808 grams (Hansen and Brange).
According to Volund et al, the material in the WHO standard is not pure insulin and contains water and salts. Based on multiple analysis they found that 1 IU = 0.034848 mg, or 1 mg = 28.696 IU. This implies 0.0036 of stabilizers (90.6% pure).
1 mole insulin = 166.8 * 10^6 IU
1 IU = 6.00 nmol
Conversion factor from µU/mL to pmol/L: 6.00
Conversion factor from pmol/L to µU/mL: 0.1667
1 pmol/L = 1 * 10^(-12) moles/L = 5.808 * 10^(-9) grams/L = 5.808 * 10^(-9) mg/mL = 5.808 * 10^(-9) * 28.696 = 166.67 * 10^(-9) IU/mL = 0.1667 µU/mL
