It is perfectly safe to take creatine with milk. There is, at least, no research or anecdotal evidence to the contrary unless an individual has lactose intolerance. The concern about taking creatine supplements with milk has more to do with its absorption and usability by the muscles than its safety.
Creatine monohydrate is a nutritional supplement taken by athletes to build muscle and enhance athletic performance. The body normally gets needed creatine from dietary sources and uses it to help fuel muscular contractions. In the body, creatine converts to creatine phosphate, with creatinine as its waste product. The goal of supplementation is to increase absorbability so that muscles absorb the maximum amount of creatine. If too much of the supplement is consumed, the excess is flushed out of the body in urine.
Supplemental creatine is available in the form of a white, tasteless powder. It must be mixed with a beverage like water, juice, or milk before consumption. Sometimes, it is shaken to thoroughly mix it before drinking. Complete dissolution is believed to merely enhance creatine’s palatability, not its absorption. Most athletes believe that taking creatine with a high-glycemic liquid, like juice, enhances its absorbability.
High-glycemic, sugary beverages stimulate the body to produce insulin, which is a factor in creatine absorption by the muscles. The glycemic index ranges from 1 to 100, with high-glycemic foods at the higher end of the scale. Taking creatine with milk is safe, but milk ranks lower on the glycemic scale, around 27 to 34. On account of this, less creatine may be absorbed if mixing it with milk than with juice, which has a glycemic ranking of 41 to 68, depending on the type of juice. This may be remedied by mixing a little sugar or honey into the creatine with milk mixture, increasing its glycemic index.
Other factors that affect creatine absorbability are temperature and the presence of caffeine. Warmer drinks cause creatine to be absorbed faster, which is why many athletes warm their creatine concoctions before drinking them. As it may be more pleasant for some people to drink warm milk instead of warm fruit juice, many athletes prefer to mix their creatine with milk. In addition, many athletes avoid drinking caffeinated beverages with creatine to enhance absorption, because a study showed that caffeine inhibits the absorption of creatine by the muscles. Many athletes are also concerned with the timing of creatine supplementation, as they need to take advantage of the insulin spike after exercise to enhance absorption.