There was a shortage of an ingredient in methylphenidate last summer, so I couldn't get refills in tablet form (allergic to gelatin capsules) and I cut back the dosage I took each day. Short-acting Ritalin wears off quickly, so I was taking (AM + PM) 20 mg Ritalin SR, which does last longer, about 6 hrs for me. Horrible emotional stuff happened when I lowered the dosage or didn't take Ritalin for a few days at a time, trying to conserve it until the shortage was over. First time I'd faced that problem-dojn't ever want to repeat it. Now, I'm on 20 mg at 7 am and 2 pm and a regular 10 mg Ritalin, right before I go to bed, to slow down my brain, so I can get to sleep. 50 mg/day works just right. I'm 62, athletic, 135 lbs, 5' 7" and have a lot of work daily on the computer. Avoid screentime for several hours before bedtime, so the brain can relax a bit.