What is considered a normal testosterone level for a 42 yo ?

Hypogonadism: There is quite a large range, and labs use different terms, but typically 400-600. There is daily and diurnal variation as well.

240 - 1200: Testosterone is different for every man and measured slightly differently at each lab. Testosterone is highest in the early am, so blood draws checking this should be done then. Also free and total testosterone are important components to understanding the level. Testosterone levels can decrease with age. Be sure to have your vit d level checked as well as low d may contribute to low t.