We do not recommend mixing the powdered milk formula with any other powders or liquids such as breast milk.
Some mothers mix powdered formula with their breast milk in order to increase the calories their baby gets during a feeding. We do not recommend doing this! This changes the composition of the breast milk and the micro-nutrients become far more concentrated. It can potentially be too much for a baby's kidneys. We recommend following the exact instructions on the formula or on our website and never mix the formula with anything but boiled water.
La Leche League International. 2016. Is it okay to mix human milk and artificial baby milk (formula)? http://www.llli.org/faq/mixing.html [Accessed December 2016]
La Leche League International. 2007. Supplementing the breastfeeding baby. http://www.lalecheleague.org/llleaderweb/lv/lvaugsep99p75.html [Accessed December 2016]
Nemours Foundation. 2015. Breastfeeding FAQs: Solids and supplementing. http://kidshealth.org/en/parents/breastfeed-solids.html [Accessed December 2016]
BabyCenter. Can I mix breast milk and formula? https://www.babycenter.com/404_can-i-mix-breast-milk-and-formula_8883.bc [Accessed January 2018]