Melatonin supplements are sometimes used to treat jet lag or sleep problems (insomnia). Scientists are also looking at other good uses for melatonin, such as: 1  Treating seasonal affective disorder (SAD).2  Helping to control sleep patterns for people who work night shifts.n most cases, melatonin supplements are safe in low doses for short-term and long-term use. But be sure to talk with your doctor about taking them. Children and pregnant or nursing women should not take melatonin without talking to a doctor first. Melatonin does have side effects.