Not sure what nan ha is, but its fine to use hungry baby formula for some feeds and not others. It doesn't have any more calories so if he's waking from hunger, having fewer calories at night could make him more hungry, you might want to up his daytime calories.
The hungry baby formula just takes longer to digest so should keep him feeling fuller for longer.
There is a sleep regression at nine months, so if this waking is more than normal, it might just pass soon anyway
Hi my son is 9 months and wakes up every 2 - 4 hours for a bottle at night and it's beginning to take it toll. I have been told I should try "Hungry Baby" formulas as they are supposed to fill bub up and keep them asleep longer, has anyone herd of these or know if they work? and is it ok to give it to bub just at night I still want to keep him on Nan H.A for his day bottles.