A circuit and method for adaptive trimming of the reference signal for sensing data during a read operation of magnetic memory cells to improve read margin for the magnetic memory cells. The circuit has a trim one-time programmable memory array programmed with offset trim data applied to magnetic memory array sense amplifiers. Sense amplifier trimming circuits receive and decode the trim data to determine offset trim signal magnitude to adjust the reference signal to improve the read margin. The method sets the offset trim level to each increment of the offset trim level. Data is written and read to the magnetic memory array, the number of errors in the array is accumulated for each setting of the offset trim level. The error levels are compared and the appropriate trim level is programmed to the trim memory cells such that a read margin of the sense amplifier is improved.