What can a fourteen year old do about constipation?

Depends: If you are otherwise healthy and on no medications, try to increase the natural fiber in your diet and drink plenty of water. Dried fruits such as prunes, plums, and the like can help. Fresh fruit and vegetables and less meat will help. One may wish to add fiber with grains or additives like bran or mucilage. Ocassionally mild laxatives are needed. Exercise helps.

Varys: If otherwise healthy and not on any chronic medications one should increase the amount of water in his/her diet. Fiber can also help, but if taking fiber there should be a commensurate increase in water.