@mtr2601 is correct that small reductions can make a big difference. Normally this is not the case as you taper down until you hit going below 10 to 15mg or so. That is the approximate level that adrenal glands most often publish cortisol when they are in charge. This is the point where adrenal insufficiency kicks in and you can start having pain that feels like a PMR flare.

If you drop from 20mg to 15mg, first that is a 25%reduction in dosage for your body and secondly that is still above the normal level that your adrenal glands function when they are operating at full force. Using that one might think you should be able to drop from 10mg to 7.5mg without problems. Few people can tolerate that large a drop at that low a dosage without pain. I designed a titrating schedule where below 10mg I dropped in much smaller amounts so I went from 10mg to 9mg, to 8.5mg to 8mg, to 7.5mg, etc. Once I hit 4mg I went down each step by 0.25mg. I stayed at each level for about 2 weeks. Pill splitting is not fun, but it worked for me.

My Rheumy was not in total agreement with my plan but willing to let me try. We had an agreement about my plans if I started having pain. It worked for me but like I said earlier we have biochemical engines and each one is a little different so we need to learn to listen to our bodies. They are in charge, not our minds when it comes to something like this.

There are good pill splitters and so-so pill splitters and bad pill splitters. My preferred design is one that holds the pill in a V-shaped pocket so the tablet fits, regardless of the tablet size. Then when I drop the blade I do it slowly with the steroid tablet since it is softer tablet and only needs a little pressure to split. Other tablets can be more compact and can tolerate more force. You should not split a coated pill, a time release pill, a caplet or anything else that might not be designed to split. You can ask your pharmacist if you have any questions, they know.