In this randomized, cross-over study 20 subjects who are undergoing testosterone (T) therapy for the treatment of T deficiency will receive both subcutaneous testosterone therapy and intramuscular testosterone therapy. One group will receive a SQ injection followed by an IM injection and one group will receive an IM injection followed by a SQ injection. The primary objective of this study is to measure testosterone concentration in men after these two treatment routes and determine if there are any significant differences due to modes of administration. Endpoints will include total serum testosterone and calculated free testosterone. A questionnaire will also be administered to assess overall patient experience with each route of administration.

Subjects planning to initiate testosterone treatment via injection at MHB will be consented into the study. Upon enrollment in the study, the randomization will be completed for each subject.

Blood collection will occur before each injection. Subjects will rate pain on the Likert scale following each injection. After treatment with the first mode of T administration (SQ or IM depending on randomization), subjects will come in for blood draws 3 days and 7 days following the injection. Two weeks after the initial injection, subjects will come in for treatment with the second mode of T administration (SQ or IM depending on randomization). Subjects will come in for blood draws 3 days and 7 days following the second injection. Two weeks after the second injection, subjects will complete an end of study assessment with an Investigator and will complete a survey assessing their satisfaction with treatment. Subjects will likely continue testosterone therapy at Men's Health Boston after completion of the study.

Inclusion Criteria:

• Ability to read, write, and understand English
• Age greater than or equal to 18
• Diagnosed with testosterone deficiency
• Pre-enrollment testosterone concentration of less than 350 ng/dL
• Planning to initiate testosterone treatment at MHB
• Willing to be followed at MHB for at least one month
• Willing to provide informed consent for this study

Exclusion Criteria:

• Previous exposure to exogenous T, clomiphene citrate, or other Selective Estrogen Receptor Modulators, unless off therapy for at least 12 weeks
• American Urological Association Prostate Symptom score of 15 or greater or significant prostatic symptoms
• History of carcinoma, tumors or induration of the prostate or the male mammary gland, including suspicion thereof
• Pre-enrollment serum PSA more than 4 ng/ml
• Serious psychiatric disease or uncontrolled medical illness, as suspected from the history or clinical examination
• Used any sex hormones or steroidal anabolic drug supplements within 28 days before pre-enrollment testosterone collection or at any time throughout the study
• Incapable of giving informed consent or complying with the protocol

Participants analyzed is 0 and 1 due to loss to follow up

AE were monitored/assessed at each study visit.

An adverse event is defined as any untoward or unfavorable medical occurrence in a human subject including any abnormal sign, symptom, or disease temporally associated with the subject's participation in the research, whether or not considered related to the subject's participation in the research. Include the type and duration of the follow-up of subjects after adverse events.