My son is 3yr 7months and his weight is 12.9 kg .please suggest medicine to increase his appetite

A. Zincovit 4ML once in a day can be given to the child for at least two months I’m so that’s definitely going to help quite a lot along with that also I’d like to tell you that you should do consult your doctor they could be another nutritional deficiencies also possibly there that is why this may be happening