Hello, Chap. I think your birth year coincides with mine. On to your question...
Before I get there, know that I am NOT a medical doctor. However, I do participate on testosterone forums (in fact, I belong to an excellent forum on yahoo which consists of men recovering from low testosterone. A few of the members there are medical doctors, as well.)
Libido is complicated, influenced by more than simply testosterone. That said, we should consider the actual results from your bloodwork. One common lab range for total testosterone is 300-1000 ng/dL. If you are "normal" (within the range) but around 400 ng/dL, you may experience problems. In conjunction with total testosterone, a measurement of free testosterone is useful. Since "free" testosterone is considered a highly bioavailable form (the form that is "free" to bind to testosterone receptors, as opposed to floating attached to other molecules), a low result in this respect might account for why you might have a "normal" total testosterone result despite low libido.
(I have read about measuring saliva tests measuring "free" DHT as well, but haven't seen blood tests available for it.) While you're posting total testosterone results, indicate the numbers for your DHEA & DHT, too. Too often doctors declare "normal" on "borderline" results, as labs are used to highlight clear cut extremes, not relative deviations. A doctor should treat a patient, not his numbers, but the numbers are helpful.
Some other factors can influence libido, such as stress, hormones like estradiol (E2- too much OR to little can dampen libido & other effects of testosterone), antidepressants or other medications, etc. Various neurotransmitters contribute to libido, which means that stimulants, SSRIs, or antianxiety drugs can derail the fine tuned balance.
If you want more information to figure out how to go about this, you could consider getting a bit more blood work done. Opt for a free testosterone test with SHBG (sex hormone binding globulin) test. A cortisol test can help shed light on stress & adrenal health. Also, testing estradiol (E2) can indicate how your body is converting testosterone &/or excreting estrogen/estradiol. (By the way, if you drink alcohol, this effects your estrogen [& by extension, testosterone] levels.) Finally, consider testing TSH (thyroid stimulating hormone), T3, & T4 (thyroid hormones). Thyroid levels can positively or negatively affect testosterone levels. Since your primary care physician probably won't see a need for these tests, you can order them for yourself through various websites. (I'm not sure if this site will let me name them). Don't obtain lab requisitions from the first site you find (as I did)- shop around for the cheapest ones. Your requisition will come with a doctor's signature, so it is legit to pursue tests this way (though they won't be covered by insurance).
By the way, you haven't run any marathons recently, have you?
Hope that helps, & sorry to load so much info in a single answer.
I took propecia for 3 years and have completely lost my libido. I stopped taking it, and regained my libido for about a week, then it has slowly declined back to zero. I am certain propecia is responsible, but I have seen many doctors and done many blood tests and can't find anything abnormal.
I quit propecia 14 months ago, and my libido is virtually non-existent. Time and time again I am told that it is all in my head. I WISH it was psychological, but its not. I have tried all these different herbs and supplements that are supposed to increase libido. No success. Really hope this is not permanent...