Low testosterone levels

Has anyone's partner suffered from this. Could you please share your experience. My SO is on the lower end of the normal range. He is now trying to lose some weight (he is a tad overweight although nothing major) and is now taking zinc supplements as well as a multivitamin. He will also start working out. Would love to hear some positive (and the less positive ones two) experiences so I dont lose hope but also know what we are facing. Thanks heaps ladies.