4. Add water to liquid-concentrate or powdered formula

If you're using liquid-concentrate or powdered formula, you'll need to add water. Follow the manufacturer's instructions for how much water to use.

You can use any type of clean water — tap or bottled — to prepare liquid-concentrate or powdered formula. If you're concerned about the purity of your water supply, talk to your baby's doctor or your water provider. Many public water systems will test drinking water upon request. If you use well water, boil it for about one minute and cool it to body temperature, 98.6 F (37 C). Measure the water after boiling it.

It's also important to consider the amount of fluoride in the water you use to prepare your baby's liquid-concentrate or powdered formula. Exposure to fluoride during infancy helps prevent tooth decay. However, regularly mixing powdered or liquid-concentrate formula with fluoridated water might increase your child's risk of developing faint white lines or streaks on the teeth (fluorosis) if these kinds of formula are your child's main source of food.

If you're concerned about fluorosis, consider ways to minimize your baby's exposure to fluoride. For example, you might use ready-to-feed formula, which contains little fluoride, or alternate between using fluoridated tap water and low-fluoride bottled water — such as purified, demineralized, deionized or distilled bottled water — to prepare concentrated formula. However, if you feed your baby only ready-to-feed formula or concentrated formula mixed with low-fluoride water, your baby's doctor might recommend fluoride supplements beginning at 6 months.