At the Doctor's Office continued...
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."
Finding the Cause
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."