A human dietary supplement comprises theacrine and optionally other compounds that modulate the effects of theacrine. Uses for the theacrine-containing supplement include improvement of at least one of mood, energy, focus, concentration or sexual desire or a reduction of at least one of anxiety or fatigue. A synergistic composition comprises co-administration of theacrine and caffeine, wherein the co-administered caffeine reduces theacrine oral clearance (CL/F) and oral volume of distribution (Vd/F). In addition, the co-administered caffeine increases area under the plasma concentration time curve (AUC) of theacrine, and increases theacrine maximum plasma concentration (Cmax) in comparison with the corresponding pharmacokinetic parameters when theacrine is administered alone.