Carnosine is formed by beta-alanine when it combines with histidine within muscle tissue. When take as Carnosine rather than beta-alanine the body breaks down carnosine in the digestive tract to beta-alanine and histidine. It then has to get reassembled in muscle cells. Beta-Alanine is more cost effective to use over carnosine.
Some users do not like the tingle that beta-alanine causes however.
Take 1.6g with your pre- and post-workout shakes. Or smaller amounts throughout the day totalling 3.2g to avoid the tingle.