I was diagnosed early last year with low T (244), after my wife complained.
The Doctor originally started me on testosterone patches; it worked reasonably well, but left my skin red and soft to where a vigorous scratch with a nail could cause significant damage. It got rid of my extreme fatigue, but didn't give me my usual energy or desire back. However, after a recheck, my T level had dropped to 133.
The doctor then moved me to *monthly* testosterone (Depo) shots. As noted by FuzzyKen above, the shot peaks after a few days and then there is a long crash until the next shot where you've got nothing and feel like shit again. After the doctor's office refused to give me the third monthly shot from my own testosterone bottle (which my insurance had insisted upon, as opposed to using the office's testosterone bottle which the doctor's office charges you an uplift fee), I was transferred to a local urologist's office to give me the shots from my own testosterone bottle.
The urologist insisted on revisiting the diagnosis and treatment, and I'm glad he did. I've been moved to Androgel, and things have dramatically changed for the better. Low energy levels are a thing of the past, and I've got my old ambition back. Still working on the desire part of the problem, and have been slowly increasing the dosage with the urologist's supervision and approval.
He explained that it takes approximately three months to stabilize at a new level, before you can tell if that level is right for you, so it's a long and frustrating grind until you get the level right. I started at 4 pumps/day of Androgel 1% (which got rid of my extreme fatigue), moved up to 6 pumps/day (feeling better, but no ambition), and then to 8 pumps/day (feel good, ambition back, but still no desire), where I've been for a two months now.
I'll be going back in next month to have my testosterone level rechecked, and to get further counseling on addressing my lack of desire. I suspect part of the problem is carrying around some excess belly fat, which I can finally address now that I've got some ambition and energy back
Don't give up. I realize now that I've had this problem of low energy and desire for the last 7 years. As does everyone else, I wanted a quick fix, but have found that it's a long slow grind until you get there. The Doctor's office didn't help by screwing me around for 8 months until I got transferred to the specialist for correct treatment.