It takes a maximum of two weeks for taste buds to grow back on a human tongue. There are many things that can cause taste buds to be lost; the most common of these occur when drinking very hot liquids, which tend to burn off the taste buds.
Some medical procedures that can also result in the loss of taste buds. These include radiotherapy, which has the potential to kill cancer cells as well as other normal cells in the body, including the taste bud cells. The taste buds on the tongue go through a two-week life cycle, which means that they are renewed every 10 to 14 days. If a person loses the ability to taste due to a loss of taste buds, the sense of taste should start returning within this two-week time frame.
If the loss of taste is due to another lesion, such as a cut in the nerve leading from the tongue to the brain, it might not be possible to determine whether the sense of taste is likely to return. In this sort of case, the loss of taste is not a result of a problem with the taste buds, but with the nerves themselves.