Dear sir thank you for your query Most babies double their birth weight at 5 months of age and triples at 1 year of age If your baby was 3 kg at birth he will be 9 kg at 12 months of age After 12 months the growth rate slightly reduces At present your son is doing okay To increase your son’s weight 1. Give him a well balanced diet including meat and eggs or paneer if you are a veggie 2. A protein rich diet 3. Avoid giving too much of cow’s milk 4. Monitor body weight regularly