Had our 12 months check up and dr said baby is under weight and referred us to a dietician. what could cause this and what can one do to up the weight. ?

Is your baby *losing* weight or just low on the weight growth curve? Weight loss or little ones who are dropping growth percentiles (particularly 2 or more) is concerning and should be monitored closely. If it's not that severe, ideas to make sure baby is getting enough include - offering whole milk and/or breast milk as the only drink options & making sure baby has protein with all 3 meals.