CMOS circuits such as OTAs (operational transconductance amplifiers) operating in the subthreshold (weak inversion) region introduce a versatile solution for the realization of low-power VLSI building blocks. In this paper, hot carrier induced degradation of electrical parameters of CMOS OTAs operating in subthreshold region is investigated by accelerated laboratory measurements. Using the experimental observations a degradation model is proposed for reliability of CMOS OTA. The advantages provided by the degradation model proposed is demonstrated by experiments on design examples of first and second order OTA-C filters. The estimated results are found in good agreement with experiments. The model proposed provides to the IC designer new possibilities to estimate the reliability of OTA-C based topologies operating in subthreshold region.