Last summer on The Dr. Oz show, the President revealed his testosterone level to be 441 (mg. per deciliter). Television's favorite medical quack called this measurement good.
In truth, a total testosterone reading of 441 is considered by most conventional standards to be fair to middlin', even for someone the President's age. Regardless, total testosterone tells us practically nothing about someone's true hormonal status, and considering specifics like "free" testosterone and "bioavailable" testosterone doesn't tell us much more because of huge variabilities in testing and other confounding factors.
In truth, the whole testosterone blood test thing is about as accurate as predicting the future using bird droppings.
The Body Doesn't Care About Total T
Testing for total testosterone by itself is ridiculous because your body doesn't care about it. What it cares about is 1) "free" testosterone, which is unencumbered to anything, and 2) albumin-bound testosterone, which, while loosely bound, is potentially available to do all the good stuff that T does. Together, they represent "bioavailable" testosterone.
The remaining 40 to 70% of testosterone in the bloodstream is tightly bound to sex hormone binding globulin (SHBG) and isn't available to your cells. That's why total testosterone doesn't tell us a thing about how well a man is functioning.
However, determining free and bioavailable testosterone is rife with problems. You can test for SHBG levels and theoretically get an idea of a man's hormonal status, but SHBG is a tricky bastard. You can be high in SHBG and have "normal" T levels, but still be deficient in bioavailable T.
You could just test for free testosterone, but the tests are horribly unreliable. A study by the Endocrine Society of America found that free testosterone levels can vary by as much as a factor of five in the same sample. You could test the same sample several times and get several different readings.
The Temporal Factor
What time of day you have your blood drawn is also tricky. The current thinking is that you need to have blood tests done early in the morning, unless you're an old or older bastard, at which point it probably doesn't matter. In younger men (those under 45 or so), testosterone levels are higher in the morning, probably peaking at about 8:00 AM and reaching their low point about 12 hours later.
Older guys don't seem to have these diurnal fluctuations, so they can have their levels tested pretty much any time before 2 PM. However, there is some evidence that early morning testing is still important for "accurate" readings on free and bioavailable testosterone, even in old guys.
Okay, so early morning testing is still, in theory, a good idea as long as your doctor is savvy enough to test for free and bioavailable T, and you somehow still believe in the integrity of the blood tests. But there's yet another factor to consider.
The Dietary Factor
Hardly anybody considers it, but what you eat before you have your blood drawn also affects testosterone levels. Some studies have shown that meals high in fat can drop T levels by anywhere from 15 to 40%. Similarly, high carbohydrate meals can drop levels from 10 to 30% for anywhere from 3 to 8 hours.
Even consuming a drink that has about 75 grams of glucose (about what you'd get in one of those "Rockstar" energy drinks) is enough to chop testosterone levels down by jaw slackening 47%.
So it appears that testing should be done fasted, but there's always a chance that being totally fasted also drops testosterone levels and prevents getting an accurate picture. There's just not enough evidence to prove or disprove it.
What's the Answer?
Go ahead, have your blood tested if it makes you feel better. Test for "total" T, free T, bioavailable T, and even SHBG. Test for estrogen, too, and see if that's high. Do it fasted and do it first thing in the morning, even if you're older. But don't necessarily treat the results as gospel. Instead, go by symptoms.
For instance, are you suffering from a lack of energy, loss of muscle tone, an increase in body fat or inability to lose weight, an inability to gain muscle, a waning libido or sexual performance problems, or frequent illness?
If so, screw the readings and try an over the counter pro-testosterone formula. Give it about six weeks, although you might see results much faster. If it doesn't give you sufficient results, go find a doctor who'll work with you in setting your hormonal boat right, regardless of what the blood tests show.