Formula
Formulas are our modern world’s version of a wet nurse. Back in the day, if a family had trouble with breastfeeding, there was always some lady in the village ready to help out and provide outside-of-mom services for helping to feed baby. Now with the emergence of newer diseases that can pass through breast milk and how mom’s milk changes as babies age, we have found a way to provide great nutrition for babies whose families can’t or choose not to breastfeed, and it’s called formula.
All standard formula is pretty much the same for a couple of reasons. The first is that it is highly regulated by the FDA (Food and Drug Administration) to provide the recommended nutritional components that pediatricians and nutritionists know babies need over the first year of life. The second is that most formula is made by 1 or 2 companies and just marketed with different labels. Oftentimes the companies that advertise the most, charge the most for their formula to make up those advertising costs, even though it is literally the same as every other brand. Another way they can make more money is to offer liquid versions of formula which are just the powdered versions mixed with sterile water. So save your money and just get the powdered version.
Most babies do just fine on the standard formula, but there are some babies who have difficulty with 1 or 2 of the proteins in formula that would normally be partially broken down in breast milk. If your pediatrician thinks there may be a dairy or formula component that does not agree with baby, they will let you know and offer other forms of formula that are more broken down into easier-to-digest elements or just contain a subset of dairy proteins. Things I look for that make me want to switch to a different formula are worsening red and itchy rashes after 6-8 weeks of age or lots of mucus or blood spots in the stool.
As for what type of water to use for mixing with the powdered formula, tap water is fine. No need for extra filtration or boiling as long as you are not on well water. Once you make the formula, it does not need to be finished right away; it can sit out for up to 4 hours at room temperature or up to 24 hours in the fridge.