D3 HD drop contains Cholecalciferol 400 IU (International units). Cholecalciferol is an analogue of Vitamin D3 which treats Vitamin D3 deficiency in children caused by inadequate exposure to sunlight and deficiency of Vitamin D3 in breast feeding mothers. 
 
Apart from this, D3 HD drop (Vitamin D3 oral drop) is specially designed for kids for:
1) Effective calcium and phosphorus metabolism 
2) Building their bones and teeth stronger. 
3) Absorption of calcium in muscles and improving muscle contraction & relaxation, flexibility & elasticity. Thus, increasing overall strength & functioning of muscles.
4) Promoting overall growth and development of kids
5) Enhancing the proper functioning of immune system, thus acting as immunity booster.
 
Use under medical supervision.