An improved double antibody radioimmunoassay for the determination of insulin in serum, plasma, and tissue incubation media.

We have modified the double antibody method of insulin radioimmunoassay to allow relatively short incubation periods and the use of centrifugation to separate bound from free insulin. This was achieved by altering the order of addition of reagents and by adding normal guinea-pig serum to reduce nonspecific interactions. The method allows for precise measurements in the range of 0-3.2 ng insulin. Both serum and plasma give consistent values. The technique is useful for the measurement of insulin levels in samples of limited size such as those from small experimental animals.