Chronic fatigue
Not recommended
Glycine is an amino acid sold as a nootropic and promoted for chronic fatigue, with the promise of restoring energy and focus. There is no solid evidence that it helps with chronic fatigue, so no proven benefit for this use. Lasting tiredness usually has a treatable cause worth finding: sleep quality and schedule, deficiencies (iron, vitamin B12, thyroid), chronic conditions, mood, so it is worth discussing symptoms with a doctor and running basic tests. Glycine is harmless in this role, but do not take it instead of proper workup and treatment that does work, or you may miss the real cause.