Vitamin D is an essential hormone for growth and development of bones in children. There is a lot of evidence for deficiency of this vitamin in Middle East females. This study conduct to find a way to combat deficiency in girls during rapid growth phase of puberty in academic year. One hundred and two Middle School girls who had not consumed any vitamins supplement have been participated in this randomized clinical trial. They allocated randomly in two case groups who received 50,000 or 100,000 IU vitamin D3 in October and three months later in January or in control group who received vitamin E. At the end of winter blood samples for 25-hydroxyvitamin D were checked. The mean of 25-hydroxyvitamin D were 5.5±1.5 ng/ml, 15.2±6 ng/ml, 23.0±6.8 ng/ml in control, 50,000 and 100,000 IU vitamin D groups respectively (P0.05). Urine calcium/creatinin ratio was equal in case and control groups (P>0.05). 100,000 IU of vitamin D3 every three months (equal to 800IU/day) can raise 25-hydroxyvitamin D above 12 ng/ml in all cases but for area with high prevalence of sever deficiency, dosage more than 100,000 IU every three months or shorter interval recommended to achieve optimal level.