LSD breaks down when exposed to oxygen and light. keep it in a totally dark container (35 mm film container) in the fridge.
From LSD, "My Problem Child" - Albert Hoffman
http://www.psychedelic-library.org/child5.htm
Only in completely oxygen-free ampules protected from light is LSD absolutely stable. Such ampules, containing 100 µg (= 0.1 mg) LSD-tartrate (tartaric acid salt of LSD) in 1 cc of aqueous solution, were produced for biological research and medicinal use by the Sandoz firm. LSD in tablets prepared with additives that inhibit oxidation, while not absolutely stable, at least keeps for a longer time. But LSD preparations often found on the black market—LSD that has been applied in solution onto sugar cubes or blotting paper—decompose in the course of weeks or a few months.