Testosterone is the primary male sex hormone and plays a vital role in men’s health. It is responsible for the development of male reproductive tissues and contributes to increased muscle mass, bone density, and sex drive. Testosterone levels peak during adolescence and early adulthood but gradually decline with age. Low testosterone, also known as hypogonadism or “low T,” affects millions of men and can significantly impact quality of life. Checking testosterone levels through blood testing is crucial for detecting low T and determining if testosterone replacement therapy may be needed. This article will provide an overview of testosterone, reasons for testing, what to expect from the testing process, and how to interpret test results.
What is Testosterone?
Testosterone is an androgen hormone produced primarily by the testicles in men, with smaller amounts secreted by the adrenal glands. It plays a pivotal role in the development and maintenance of male reproductive and sexual function. Testosterone is responsible for the emergence of secondary sex characteristics during puberty, including:
- Growth of body and facial hair
- Deepening of the voice
- Increased muscle mass and strength
- Increased bone density
- Growth of the testicles and penis
In adulthood, testosterone continues to support libido, sperm production, muscle mass, bone density, red blood cell production, fat distribution, and cognitive function.
Why Test Testosterone Levels?
There are several reasons testing testosterone levels may be recommended:
Signs and symptoms of low testosterone
If a man exhibits symptoms that indicate declining testosterone, testing levels can help confirm or rule out low T as the cause. Symptoms may include:
- Reduced sex drive and erectile dysfunction
- Loss of muscle mass and strength
- Increased body fat and diminished endurance
- Fatigue, irritability, and depression
- Loss of body and facial hair
- Decreased bone mineral density
- Difficulties with concentration and memory
- Reduced testicle size
Routine screening
The Endocrine Society recommends screening for low testosterone in men over age 65 who have signs or symptoms, as well as those over age 70 regardless of symptoms. Screening may also be advised for men under 65 who have chronic health conditions or risk factors associated with lowered testosterone.
Monitoring testosterone therapy
For men undergoing testosterone replacement therapy, whether by injections, gels, patches, or pellets, regular testosterone testing helps ensure dosage is optimized. Too high or too low testosterone during treatment can cause side effects.
Infertility evaluation
Since testosterone is vital for healthy sperm production, low levels may contribute to infertility. Checking testosterone along with other hormones can uncover hormonal imbalances impeding fertility.
Delayed or precocious puberty
Testosterone levels are evaluated when a boy has absent, incomplete, or late onset of puberty. Elevated testosterone in young boys before age 9 may signal precocious puberty requiring treatment.
Hypothalamic or pituitary disorders
The hypothalamus and pituitary gland regulate testosterone production by the testes. Tumors, inflammation, or other abnormalities affecting these glands can lead to low testosterone. Testing helps determine if the root cause is primary or secondary hypogonadism.
Genetic disorders
Genetic conditions like Klinefelter syndrome, Kallmann syndrome, or pituitary disorders may disrupt normal testosterone levels and production. Testing can confirm the diagnosis.
Preparing for the Test
Certain preparations may be recommended before your testosterone test:
- Fasting – Fasting for 8 to 12 hours prior helps avoid spikes right after eating.
- Morning testing – Levels peak in the morning so testing is often scheduled before 10 am.
- Limiting medications – Anabolic steroids, glucocorticoids, and anticonvulsants may affect results.
- Refraining from sex/exercise – Both can temporarily increase testosterone for up to an hour beforehand.
Be sure to discuss any supplements, prescription medications, or over-the-counter drugs you’re taking as some may alter results. Your doctor will inform you of any preparations needed for the test.
The Testing Process
A simple blood test is all that is required to measure testosterone levels. The steps are as follows:
- The site for blood draw will be cleaned usually the arm.
- A tourniquet is applied to make the veins more visible.
- A needle is inserted into the vein and blood is collected into attached vials, usually requiring 1-2 tubes.
- The tourniquet is removed, the blood draw site is bandaged, and labeling applied to the vials.
- The blood sample is sent to a lab for analysis.
Some key points about the blood draw:
- It takes only a few minutes to collect the sample.
- You will feel a slight pinch when the needle goes in.
- Holding your arm straight allows easier access to the vein.
- Bruising or discomfort may occur but typically resolve quickly.
Levels of total, free, and bioavailable testosterone can be measured from the blood sample. Total testosterone includes both bound and unbound hormone while free testosterone represents the amount circulating freely. Bioavailable testosterone encompasses both free and loosely bound forms.
Understanding Test Results
Testosterone lab results will include the measured level along with the normal range based on your age:
Normal testosterone levels
| Age Group | Normal Total Testosterone Level |
|---|---|
| 0-5 months | 75-400 ng/dL |
| 6 months – 9 years | <7 ng/dL |
| 10-11 years | <7-130 ng/dL |
| 12-13 years | 7-800 ng/dL |
| 14 years | 100-1,200 ng/dL |
| 15-16 years | 300-1,200 ng/dL |
| 17-18 years | 400-1,000 ng/dL |
| Over 19 years | 240-950 ng/dL |
Results are typically reported in nanograms per deciliter (ng/dL) or nanomoles per liter (nmol/L).
Low testosterone
A testosterone level below the normal range indicates hypogonadism or low T. This threshold varies slightly between laboratories but is generally below 300 ng/dL. Low T may be categorized as:
- Total testosterone under 200 ng/dL – consistent with pathological hypogonadism
- Total testosterone 200-300 ng/dL – suggestive of hypogonadism based on symptoms
- Free testosterone under 5-9 pg/mL – typically considered low T
Your doctor will interpret your lab results and advise if they indicate low testosterone. A repeat test may be needed to confirm.
High testosterone
Elevated testosterone over 1000-1200 ng/dL is considered abnormally high. Potential causes include:
- Use of testosterone therapy at supratherapeutic doses
- Androgen abuse or use of anabolic steroids
- Adrenal gland disorders
- Testicular tumors
- Inherited conditions causing gonadal hyperfunction
High testosterone results should be investigated by your physician to identify any underlying condition requiring treatment.
Next Steps After Testing
Your doctor will explain your testosterone test results and what they mean for your health. Some examples of next steps include:
Repeat testing
If your results are abnormal, repeating the test 1-2 more times will help confirm or rule out an issue with testosterone production.
Further evaluation
Additional blood tests may be ordered to pinpoint the cause of low or high testosterone. For low T, this includes checks for pituitary function and related hormone levels.
Imaging tests
If pituitary dysfunction is suspected, an MRI of the pituitary gland may be recommended to check for tumors or structural abnormalities. For high T, testicular ultrasound can check for masses.
Referral to a specialist
Your primary care provider may refer you to a urologist, endocrinologist, or fertility specialist for further assessment and treatment guidance.
Testosterone therapy
If low T is confirmed and symptoms are significantly impacting quality of life, testosterone replacement therapy may be prescribed. This can greatly alleviate low T symptoms when properly managed.
Treatment of underlying condition
For abnormal testosterone related to a medical condition, treatment will focus on addressing the underlying cause. This may include surgical removal of a testicular or adrenal tumor.
Conclusion
Getting tested is crucial for any man concerned his testosterone levels may be off. Symptoms of low T should prompt laboratory testing to accurately measure total and free testosterone and uncover a potential hormone deficiency. Treatment can then be implemented to reverse symptoms and improve health outcomes related to muscle, bone, sexual function, mood, energy, and more. With hormone replacement therapy or management of underlying medical conditions, low testosterone does not have to reduce quality of life. Being proactive about testing provides the key information needed to take appropriate action.