Litchi sweet is due to its high sugar content. Different varieties of sugar content varies greatly, March red litchi varieties of sugar content is low, about 16%; and sticky rice cake litchi varieties of sugar content is high, up to 19.2%. Sugar in lychee is mainly sucrose (5% to 12%), fructose (3.5% to 6.5%) and glucose (3.5% to 6.0%). Diabetic patients to take sugar-rich lychee must be very careful, sugar metabolism is normal people can eat lychee.

There are also cases where the consumption of lychee leads to a decrease in blood glucose, resulting in hypoglycemia caused by the so-called "lychee disease". The "fire" phenomenon of some lychee varieties may be an inflammatory reaction, and they are only manifested in individual people. These people can try different varieties of lychee fruit.