Will dhea 25 milligram increase muscle mass if supplemented once a day?

Yes it could: Dhea could potentially increase your testosterone leading to higher lean body mass and lower fat mass. However, pure dhea might increase your Estradiol levels as well which in higher doses can cause gynecomastia (male breasts) and other estrogen related side-effects. I suggest taking 7-keto dhea rather than pure dhea to prevent raise in other hormones since it won't convert to estrogen.