Help please? How old do you have to be to get chin liposuction?

See your doctor. Liposuction is done under the chin usually with the neck area and jowels. See your medspa doctor to discuss what is appropriate for you. You are certainly old enough but the medspa doctor may also show you some noninvasive skin firming and tightening radiofrequency options that may take care of your issue.
I don't recommend liposuction for the area under the chin. Removing the fat in the submental or neck area is better done by direct excision through a small incision under the chin. This allows the surgeon to remove the fat from on top of the muscle and under the muscle where it is often located. Under the muscle cannot be addressed in any other way. This approach also allows the skin to be lifted from the muscle and the muscles reapproximated and tightened so that the skin can drape in a better way and restore the angle of the neck.
Usually at least 18. I do not think liposuction should be done on children. Diet and exercise is the safest way to contour our body. However, as we age there are areas that do not respond to diet and exercise and these areas are prime candidates for liposuction.