A: You may be tempted to buy bottled water to mix with formula, but in general, tap water is safe. In fact, since there aren't clear standards for the filtering process used in bottled water's production, it may not be any better than your local tap water and could be worse. Bottled water also lacks fluoride, important for healthy teeth, so if you use it, ask your doctor about starting baby on fluoride drops at 6 months.Whatever kind of water you use, it's best to sterilize it first. Bring the water to a running boil for one minute and then turn it off. If you let it boil for too long, concentrated salts and minerals can build up. You can stop sterilizing water once you've introduced your baby to solid food, at 4 to 6 months, since your child's system will be exposed to bacteria in real food.When preparing formula, be sure not to add more or less water than recommended. If formula is too diluted, your baby will be undernourished; formula that's too strong can dehydrate your baby. Concentrated liquid formulas should be mixed with an equal amount of water, and powdered formulas require measuring out a specific amount of water. Ready-to-feed formulas, of course, don't require any additional water. --Emily Bloch
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