Hello . I M In Process Of Weight Reducition. I

hello . i m in process of weight reducition. i go to gym regularly. now a day i found my skin turning black as if lifeless. i was been told by my frien to take vitiman d . so i asked chemist he gave me cipcal 500. can u pl tell me if i is ok to take 1 tablet per day for 1 mth. i m 42 yes old