If you’re experiencing signs and symptoms of low testosterone mentioned above, talk to a healthcare provider. Your doctor will ask about your symptoms and evaluate you, and may order blood tests or refer you to an endocrinologist or urologist.
If your child was assigned male at birth and isn’t showing signs of puberty by the age of 14, talk to their pediatrician, notes Cleveland Clinic.
Hypogonadism and age-related low testosterone are diagnosed with blood tests that measure the level of testosterone in the body.
The Endocrine Society
and the American Association of Clinical Endocrinologists
recommend testing for suspected low T with a total testosterone test performed in the morning (when testosterone levels tend to be highest in young men, although this isn’t necessarily the case in older men).
The blood test should be done after an overnight fast.
The test is often repeated on another day if the results show a low T level.
The majority of testosterone in the blood is bound to one of two types of protein — either albumin or sex hormone binding globulin (SHBG) — while a small percentage is unbound, or free.
The portion of testosterone that is bound to SHBG is biologically inactive but, because the bonds between testosterone and albumin are weaker than those between testosterone and SHBG, the portion bound to albumin is biologically active. Bioavailable testosterone therefore includes free testosterone and albumin-bound testosterone.
A total testosterone test, the most common type of test, measures free testosterone and testosterone that’s attached to proteins. A free testosterone test, which is less common, measures only the biologically active form of testosterone. This test is less common, as is a bioavailable testosterone test which measures free testosterone and testosterone that’s loosely attached to a blood protein called albumin.
A number of medical conditions and medications can raise or lower the amount of SHBG in the blood, consequently altering the amount of bioavailable testosterone. Conditions that can raise levels of SHBG can be related to liver disease, hyperthyroidism, and reduced production of sex hormones (in males). Low levels of SHBG may be related to hypothyroidism, type 2 diabetes, obesity, and polycystic ovary syndrome (in females).
In those situations, measuring the amount of bioavailable testosterone gives a more accurate indication of the amount of biologically active testosterone in a person’s system.
Other blood tests you may be given to diagnose low testosterone include:
- Luteinizing hormone (LH) blood test can help determine if an issue with your pituitary gland is causing low testosterone.
- Prolactin blood test measures levels of prolactin, a hormone responsible for lactation. High levels may be a sign of pituitary gland issues or tumors.
- Iron level test is used to rule out hemochromatosis, a disorder in which extra iron builds up in the body, causing symptoms like fatigue, joint pain, loss of interest in sex or erectile dysfunction.
