Hello and welcome to HCM,
At the age of 18, the growth plates of long bones fuse and the lengh of long bones does not increase and thus practically there is no increase in height.
I suggest you to not to take medication which claim to increase height since they have severe side effects without affecting the height.
Fusion of growth plates take around
puberty and puberty is attained around age of 11-13 in girls and 12-14 in boys.
Beyond the age of puberty, growth of long bones stops due to fusion of growth plates.
Illazarov technique is a technique wherein the long bones are artificially broken and stretched with a special device.
However, this technique is not commonly practiced, is painful and results are obtained after a very long period.
You can consult an orthopedician for more details.
Thanks and take care
Dr Shailja Puri