A low testosterone test starts with a total testosterone drawn fasting between 7 and 10 a.m., repeated on a second morning if the first is low. Guidelines generally use a total testosterone under about 300 ng/dL on two morning tests, together with symptoms, to diagnose low testosterone. One number is not enough: free testosterone, SHBG, LH, FSH, and prolactin tell you whether the level is truly low and where the problem comes from. Through August, the full workup can be drawn at home in the morning, with results typically the next day and clinician review.
Key takeaways
• Two morning fasting total testosterone results under about 300 ng/dL, with symptoms, is the usual threshold.
• Free testosterone and SHBG catch cases total testosterone misses.
• LH and FSH show whether the testes or the pituitary are the cause.
• Prolactin, TSH, and a metabolic panel rule out other explanations.
Symptoms that prompt testing
Low libido, erectile difficulty and fewer morning erections, fatigue, loss of muscle and strength, increased body fat, low mood or irritability, poor concentration, reduced body hair, and infertility. Many of these overlap with sleep problems, depression, thyroid disease, and medication side effects, which is why the workup checks more than testosterone.
What to ask for
1. Total testosterone, fasting, 7 to 10 a.m., repeated once if low
2. Free testosterone (or calculated free T) and SHBG, because binding proteins change how much is usable
3. LH and FSH, to locate the cause
4. Prolactin, which suppresses testosterone when high
5. TSH, since thyroid disease mimics the symptoms
6. CBC and metabolic panel, for general health and before any treatment
7. PSA for men over 40 to 50 or before testosterone therapy
8. HbA1c and lipids, since metabolic disease and low testosterone travel together
The hormone panel for men bundles these, and the testosterone test guide covers the central marker.
Reading the numbers
Ranges vary by lab. Morning total testosterone reference ranges typically run from about 300 to 1,000 ng/dL. Common patterns:
• Total under 300 on two mornings, high LH and FSH: primary hypogonadism (testes); causes include injury, chemotherapy, genetic conditions, age
• Total under 300, low or normal LH and FSH: secondary hypogonadism (pituitary or hypothalamus); causes include obesity, sleep apnea, opioids, steroids, high prolactin, illness
• Total normal, free low, SHBG high: functionally low testosterone, common with age, liver disease, or thyroid excess
• Borderline total with symptoms: repeat, add free testosterone, and address sleep, weight, and alcohol before concluding
See testosterone test results explained for detail.
What to do before concluding you are low
Fix sleep, lose weight if applicable, cut alcohol, and review medications, especially opioids and steroids. These raise testosterone in many men and are required before any therapy decision. Confirmed low testosterone with a clear cause is a different conversation, and one for a clinician.
Preparing for the test
Fast overnight, draw between 7 and 10 a.m., sleep normally the night before, skip hard training that morning, and pause biotin for two days. See do you need to fast for a testosterone test.
Testing with August
Order the men’s hormone panel from the August lab tests catalog, book an early at-home draw, and get results typically the next day with clinician review. One all-inclusive price, no membership required. August Care members ($29 a month, cancel anytime) get up to 50% off next-day lab tests, a first clinician consultation included, later consultations at $19, and AI action plans on results. A consultation is the right place to interpret the pattern and discuss options.
Frequently asked questions
What test diagnoses low testosterone?
A fasting morning total testosterone, repeated if low, interpreted with symptoms and with free testosterone, SHBG, LH, FSH, and prolactin.
What testosterone level is considered low?
Commonly under about 300 ng/dL on two morning tests, varying by lab and guideline.
Why does the test need to be in the morning?
Testosterone peaks early and falls through the day. Reference ranges are based on morning samples.
Why test free testosterone?
Because SHBG binds testosterone and can make total look normal while usable testosterone is low.
What do LH and FSH show?
Whether the cause is in the testes (high LH and FSH) or the pituitary and hypothalamus (low or normal).
Can low testosterone be reversed without medication?
Often improved: better sleep, weight loss, less alcohol, and treating sleep apnea or stopping offending medications.
Can I test for low testosterone at home?
Yes. An August phlebotomist draws the sample at home in the morning, with results typically the next day.
Does August Care discount testosterone testing?
Yes. Members get up to 50% off next-day lab tests and a first clinician consultation included.
