Had a blood test that showed low vitamin d (17.5) and low testosterone (284). could these be related? i am a 31 year old male.

Possibly: There is some research, largely done in animals, where receptors for the action of vitamin D in various tissues were "knocked out." When vitamin D was "knocked out", sperm count was sometimes reduced. Also noted is some seasonal variation in testosterone levels being lower in the winter, like vitamin D is when there is less sun exposure. Recommended daily intake is 400-600 IU daily