Disclosed herein are salts and solid forms of 4-hydroxy-N,N-diisopropyltryptamine hemi-glutarate (4-OH-DIPT), e.g., 4-OH-DIPT hemi-glutarate, 4-OH-DIPT hemi-succinate, 4-OH-DIPT hemi-succinate hydrochloride, and 4-OH-DIPT hemi-glutarate hydrochloride. The solid form may be a salt and/or a crystalline form of the 4-OH-DIPT, such as a polymorph of 4-OH-DIPT or a salt thereof. Also disclosed are methods for making the solid forms and methods for administering the solid forms. The disclosed solid forms of 4-OH-DIPT are useful for treating neurological disease and/or a psychiatric disorder in a subject.