Overview
Testosterone is a hormone produced primarily in the testes in men and the ovaries in women. Testosterone is connected to sexual development, muscle building, fat loss, some aspects of cognition, and hair loss.[1]
Your testosterone levels may not tell the whole story of how testosterone is functioning in your body. Total testosterone can be divided into three categories.[2]
Tightly bound testosterone: About two-thirds of the testosterone in your blood is bound to sex hormone binding globulin (SHBG). It is not readily available for use by your body.
Loosely bound testosterone: About one-third of the testosterone in your blood is weakly bound to albumin. Once the bond is broken, the testosterone circulates as free testosterone in your body.
Free testosterone: A small percentage of the testosterone in your blood (1–4%, as a rule) floats around freely. Your body can readily use it, and the enzyme 5-alpha-reductase can convert it to dihydrotestosterone (DHT), a very potent androgen.
Together, your loosely bound and free testosterone compose your bioavailable testosterone, which has a greater impact on your health than your total testosterone.
How are testosterone levels assessed?
A blood test is used to assess testosterone and its components (free T, bound T, etc). Abnormally low or high levels can cause health issues in males and females.
When your T levels are tested, the reference range can vary a lot from lab to lab. A recent study showed that the bottom of the range for males can be 5.55–10.4 nanomoles per liter, or nmol/L (160–300 nanograms per deciliter, or ng/dL), and the top of the range can be 25.17–39.18 nmol/L (726–1,130 ng/dL).[3] So if you get measured at 280 ng/dL, you may or may not be considered as having “low testosterone”.[3]
Because testosterone levels can fluctuate throughout the day, the test should be performed in the morning (8–11 a.m.). If the results come back low, a second test can be ordered to confirm the first result. As part of the workup, your physician may also measure your levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and the T4 thyroid hormone (thyroxine) to get an accurate diagnosis.
What are the symptoms of abnormal testosterone levels?
The symptoms vary between males and females. The table below lists the more common manifestations.
| LOW T | HIGH T |
|---|---|
Delayed puberty | Congenital adrenal hyperplasia |
High blood pressure | |
High heart rate | |
Excess breast tissue (gynecomastia) | Possible tumor in the adrenal glands |
Hair loss | Possible tumor in the testicles |
Increased body fat | |
Issues with fertility | |
Issues with pituitary gland | |
Loss of muscle mass | |
Low libido / sex drive | |
Low sperm count | |
Poor bone health | |
Stunted growth |
| LOW T | HIGH T |
|---|---|
Abnormalities with menstrual periods | |
Issues with fertility | Congenital adrenal hyperplasia |
Excess body and facial hair | |
Increased muscle mass | |
Polycystic ovary syndrome (PCOS) | |
Possible tumor in the adrenal glands | |
Possible tumor in the ovaries | |
Voice deepening | |
What affects testosterone?
Supplements
Try to get enough vitamin D, zinc, and magnesium in your diet, as these are key nutrients for supporting healthy testosterone levels. However, if dietary changes prove insufficient, supplementation can help make up the difference.
But supplements can’t replace a healthy lifestyle. To optimize your testosterone production, make sure you get enough quality sleep, incorporate some resistance training into your workout program, and monitor your weight.
The table below displays an analysis of human studies and indicates how supplements may affect testosterone.
If you are looking for a complete, precise, step-by-step guide on supplementing for optimal testosterone production, we recommend you look at our Testosterone Supplement Guide.
It’s based on science, not marketing hype. Best of all, it comes with free lifetime updates (and is backed by an unconditional 100% money back guarantee).
Sleep
Lack of sleep can notably decrease testosterone production[4][5][6][7][8] and facilitate fat gain[9] (which itself can impair testosterone production).
Weight management
Fat gain and its associated chronic diseases, such as cardiovascular disease and type 2 diabetes,[10][11][12] are strongly linked to decreases in testosterone, particularly in middle-aged and older men.
If you gain weight — fat, not muscle — your testosterone production can drop. Fortunately, if you lose fat, your testosterone production can climb back up.
Both observational studies[10] and randomized controlled trials (RCTs)[13] have shown consistent results: in males who carry excess fat tissue, the greater the weight loss, the greater the testosterone increase.
A meta-analysis of 24 RCTs looked at weight loss as a result of diet or bariatric surgery in males.[13] In the diet studies, the average 9.8% weight loss was linked to a testosterone increase of 2.9 nmol/L (84 ng/dL). In the bariatric-surgery studies, the average 32% weight loss was linked to a testosterone increase of 8.7 nmol/L (251 ng/dL).
You don’t need to lose huge amounts of weight to see a bump in your testosterone levels either. Males that reduce weight by just 5% can increase total testosterone by 2 nmol/L (58 ng/dL).[14]
Exercise
Resistance training can raise testosterone levels for 15–30 minutes after exercise.[15][16] More important, it can benefit testosterone production in the long run by improving body composition and reducing insulin resistance.[15]
Overtraining, however, is counterproductive. Prolonged endurance training especially can cause your testosterone to drop.[17][18] Ensuring adequate exercise recovery time will help you reap the full benefits of physical activity.
Age
Middle-aged[19] and older[20] males see their total testosterone levels decrease by 0.4% to 1.6% per year, many of whom had lower-than-average levels even in their 30s.[21] Bioavailable testosterone decreases by about 2–3% a year.[19]
Those numbers can be pretty misleading though. Men approaching middle age tend to exercise a lot less and eat a lot worse. So it’s hard to say what a “natural” decline in testosterone looks like on a population-wide basis.
It’s kind of like saying muscle mass decreases 1–2% a year once you hit middle age. That decrease can have a lot to do with more time spent on work and family and less time spent trying to get ripped.
Medical conditions
Hypogonadism, when the body’s sex glands (testes, ovaries) underproduce hormones, is a prominent cause of abnormal testosterone levels. There are many potential causes of hypogonadism.
Age
Cancer (particularly when treated with chemotherapy and/or radiation)
Disorders of the testicles
Genetic disorders (Turner’s syndrome in females and Klinefelter’s syndrome in males)
Hypothalamus-pituitary-axis disorders
Infections
Liver and kidney diseases
A deficiency in the enzyme 5-alpha-reductase, which converts testosterone to the more active dihydrotestosterone (DHT) form, will present as low T levels and/or abnormal genitalia formation at birth due to the lack of DHT.
In females, polycystic ovary syndrome (PCOS) can elevate levels of androgen hormones, including testosterone (T), free testosterone, dehydroepiandrosterone (DHEA), and DHEA sulfate (DHEAS).[22] These elevated levels can cause body-hair growth, acne flare-ups, and a type of hair loss more consistent with male-pattern hair loss than female-pattern hair loss.
Drugs
DRUGS THAT INCREASE TESTOSTERONE
Testosterone replacement therapy (TRT) is a prescription testosterone treatment for increasing T levels. It’s commonly used for males with low T and transgender males, but may also be used for primary hypogonadism, metastatic breast cancer, delayed puberty, and hypogonadotropic hypogonadism.
TRT can be delivered in a variety of ways.
Buccal tablet (dissolves in the mouth)
Injection into the muscle or subcutaneous tissue
Nasal gel
Oral capsule
Subcutaneous implant
Topical gel or solution
Transdermal patch (worn on the skin)
TRT may cause side effects and increase certain health risk factors, which should be monitored by your physician.
| LOW TO MODERATE | SERIOUS TO SEVERE | UNCLEAR |
|---|---|---|
Blood clots | Heart attack risk | |
Back pain | Difficulty breathing, especially during sleep | Prostate cancer risk |
Breast enlargement or pain | Enlarged prostate, leading to difficulty urinating | Stroke risk |
Erections that last too long | ||
Erections that occur too frequently | ||
Increased cholesterol | Large mood changes, including depression, anxiety, or suicidal thoughts | |
Issues with fertility | Lower leg pain, swelling, warmth, or redness | |
Injection site irritation | Nausea or vomiting | |
Joint pain | Pain in the upper right part of the stomach | |
Moderate mood swings | Problems with urination | |
Sleep problems | Swelling of the hands, feet, ankles, or lower legs | |
Voice deepening | Worsening heart failure | |
Voice hoarseness | Yellowing of skin or eyes | |
Drugs that inhibit CYP19A1, the aromatase enzyme, are indirect testosterone boosters in males. CYP19A1 serves many purposes, one of which is to convert testosterone to estradiol, the predominant form of estrogen. Inhibiting this enzyme reduces the percentage of testosterone that gets converted to estradiol.
It may seem counterintuitive, but the male body needs estradiol,[23] though in a lesser quantity than females need. When the body detects that estradiol levels are too low, it reacts by increasing its production of the base material it needs to make estradiol: testosterone.
DRUGS THAT DECREASE TESTOSTERONE
Several drugs and drug classes may decrease testosterone levels. If you are on any of the medications below and are concerned about your T levels, consult your physician. Do not stop the treatment without professional medical input.
Antiandrogens (e.g., cyproterone, bicalutamide, flutamide, spironolactone)
Chemotherapy (e.g., alkylating agents)
Chronic anabolic steroid use (particularly when high doses are used)
Glucocorticoids
Ketoconazole
Luteinizing hormone-releasing hormone agonists (aka LHRH analogs or GnRH agonists)
Opioids
Radiation therapy (total body or pelvis in particular)
Selective serotonin reuptake inhibitors (SSRIs)
Suramin
