Tell your doctor right away if you have any serious side effects, including: mental/mood changes (such as anxiety, depression, increased anger), trouble sleeping/snoring, signs of serious liver disease (such as persistent abdominal pain/nausea, unusual tiredness, yellowing eyes/skin, dark urine). Most men using testosterone therapy notice a slight increase in their aggressiveness but because these side effects were found in men taking oral testosterone (causes liver problems which leads to skin color changes) or abusing testosterone, it is unlikely these will be an issue for you.
According to authors of a 2008 study published in the Journal of Clinical Endocrinology, testosterone therapy may even induce sleep apnea. Researchers studied five hypogonadal (testosterone deficient) men to determine the whether testosterone therapy may play a role in sleep apnea. After six weeks of treatment, obstructive sleep apnea developed in one man and markedly worsened in another in association with testosterone administration. Both also had significantly decreased oxygen levels and developed cardiac arrhythmias during sleep. How to treat sleep apnea is out of scope for this article but a quick google search can help you find information on how to diagnose and treat sleep apnea.
Since doctors know that one of the best ways to prevent what are the side effects of testosterone injections is to fastidiously avoid exceeding the appropriate dosage, it is highly unlikely that any patient will be prescribed more than what is necessary to restore normal testosterone levels. To further prevent what are the side effects of testosterone shots once the therapy cycle has ended, physicians will typically taper off the dosage. If the patient relies on an established and fully credentialed medical professional for their Low T treatment, they can expect the cost of their prescribed injections to be reasonably and competitively priced.