Q&A: Should I dilute a bottle with water to help stop the night time feedings?

The answer to your specific question of whether one diluted feed per day will harm your child's health is no, not in an otherwise healthy six-month-old. She will end up unsatisfied and her smart kidneys will rid her body of excess water.

Diluting her feeds by 50% every time is a different story. In this case, a six-month-old taking in 30 ounces per day and ordinarily getting 600 calories would only get 400 calories, a significant difference. A healthy older infant would be hungrier and adjust her appetite to take in more. A very young or sick infant who doesn't have the energy to eat that much more, or one whose kidneys can't process the excess water might end up not growing, or with a potentially dangerous salt/water imbalance.

The bigger issue is why do it at all?

Most six-month-olds demand a bottle at night, not because they need the nutrition --or even because they are hungry-- but because that is the pattern they've become used to, waking and getting a bottle to get back to sleep. A better way to stop this habit is to stop the night bottle altogether. Families who don't like this more drastic method can substitute plain water in a night bottle, which will at least spare Baby's teeth from the decay brought on by bathing teeth at night in the sugars that milk contains.

Substituting another object of comfort besides the bottle, such as a 'safety' blanket or toy, for example, can help make the transition off the bottle easier.