Why testosterone? Are you trying to body build beyond your body's natural limits?
In my opinion, DHEA is more useful for UC than testosterone. It gives the body the option of converting to the sex hormones it needs, while leaving enough original DHEA to perform other functions like wound and tissue healing. Testosterone is downstream and all it converts into is DHT, which is very powerful and at your age you'd need to be careful. At least by taking DHEA, there is slightly less risk of this.
At your age, the body makes about 15-20mg of DHEA every day, naturally. It then converts it to sex hormones as needed. If you take prednisone for a long time, natural DHEA production will stop... which is why people start suffering bone degeneration, mood swings, and other symptoms. DHEA is responsible for taking care of those things. If you're on prednisone, you could supplement with DHEA. If you're off prednisone and your adrenals are functioning normally, I don't see why you'd take DHEA or testosterone at all other than for artificial performance enhancement.
If you're going to take testosterone boosting drugs off and on, you will want to get blood work done. In principle I can't condone use of those hormones at your age, you're just playing with fire and it could screw up your endocrine system. Having said that, I know a lot of young men have bodybuilding ambitions, so much that it becomes a hobby for them... so do what you will.
If you're on prednisone, up to 25mg DHEA is probably OK for you. If you're off it, then reduce to 10mg DHEA. If you start having sleep troubles, aggression, ridiculous libido, feel jittery and anxious, then you need to reduce the dose or consider stopping.