First of all, the diagnosis of low testosterone levels should be confirmed with the proper use of lab testing. Blood testosterone levels fluctuate throughout the day, peaking early in the morning and reaching a low point in the evening. Additionally, there are multiple available blood tests used to measure testosterone; typically the assay that measures total testosterone instead of just the "free" testosterone is more reliable. You should make sure that your level was discovered using the right test at the right time of day. If it was low, it should also be repeated to confirm the result.
If the proper testing does show a low level and this is confirmed, then further testing is warranted to determine the cause of the low testosterone. More blood work in addition with a thorough physical exam can help figure out if the problem is under-secretion of hormones from the brain or if it is a primary issue related to underproduction of the hormone from the testicles. Your primary care doctor
can help you figure out these issues and suggest treatment. If testosterone replacement is prescribed, it may be given as injections, topical gels, or oral medication.