Diagnosing Low Testosterone

Medically Reviewed by Stuart Bergman, MD on August 27, 2015
3 min read

If you're an adult man and you're wondering if you have a low testosterone (low T) level, there are some symptoms to look for.

If your testosterone levels drop below normal, your sex drive may lessen. You may also be less able to get and maintain an erection.

But low T can also cause many symptoms unrelated to sex. Low testosterone levels can:

  • Lower your energy levels
  • Cut your drive to get things done
  • Make you more irritable

You may also find it tougher to concentrate. And your risk of depression may rise.

Low testosterone can lead to changes in your body, too. For example, you may:

  • Grow less body hair
  • Have a decline in muscle mass
  • See an increase in your breast size

Low T can also cause osteoporosis, which gradually weakens your bones, leaving them brittle and at risk for breaks.

Testosterone is also important for muscle health.  Low T can cause muscle atrophy, which can also lead to increased risk of falling.  The heart is a muscle too and needs testosterone.  

As testosterone levels drop body fat increases, which can increase the risk for diabetes.  

"Men should be aware of these symptoms and think about low testosterone," says endocrinologist Spyros Mezitis, MD, PhD, of Lenox Hill Hospital in New York City. "Physicians have to think about it as well. It remains under-diagnosed and it's not part of a routine checkup."

But these symptoms can also be related to other conditions. Make an appointment with your doctor, who can do some tests to see what's causing your symptoms.

When you go to the doctor with symptoms of low T, your doctor will:

  • Go over your medical history
  • Discuss medications you take (prescription and non-prescription)
  • Ask you about any family or relationship problems

"We want to look for other possible sources of the symptoms," says Jason Hedges, MD, PhD. Hedges is a urologist at Oregon Health and Science University in Portland. "Other things can lead to these symptoms, including your job, stress, and everyday life."

You will also have a physical exam. Your doctor will examine your body hair, testicles, penis, scrotum, and breasts.

Finally, your doctor will take a blood sample to measure your testosterone level. Your doctor may want to do the blood test first thing in the morning, when most men's testosterone levels are at their highest.

The normal range for total testosterone is between approximately 300 and 1,000 nanograms per deciliter. If you fall below that range and have symptoms of low T, the diagnosis is fairly certain.

However, symptoms can happen even if you have normal levels of total testosterone. If that's the case, your doctor will likely measure "free" and "bioavailable" testosterone. These types of testosterone make up a small portion of your total testosterone. But knowing their levels can offer helpful clues about how well your body is making testosterone. Some doctors will measure all three types of testosterone at the same time.

Hedges says making a diagnosis can require more than just following the numbers.

"You don't just treat the level, you treat the patient," he says. "If you have symptoms but are at the low end of the normal range, I would be willing to try to increase those levels to see if the symptoms improve."

If you are diagnosed with low testosterone, other tests may be needed to get at the cause. For example, your doctor may order imaging tests to see if your pituitary gland and testicles are working properly, Mezitis says. "At that point, a specialist should be involved."

Just don't be surprised if that specialist is unable to determine the reason your testosterone has dropped.

"The job of the physician is to look for causes," says Hedges, "but often there isn't any to be found and patients are kind of left with, this is the way it is and I don't know why."

Show Sources


Spyros Mezitis, MD, PhD, endocrinologist, Lenox Hill Hospital, New York City.

Jason Hedges, MD, PhD, urologist, Oregon Health and Sciences University, Portland.

Patient Education Institute: "Low Testosterone."

Hormone Foundation: "Patient Guide to Testosterone Therapy in Adult Men with Androgen Deficiency Syndromes."

Osvaldo, P. JAMA Psychiatry, March 2008.

Wang, C. Diabetes Care, July 2011.

News release, University of California, San Diego.

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