@prestol
"My question is: wouldn’t my adrenals have slowly recovered once I got below 5 mg? I did a long slow taper."
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Dose and duration and perhaps "cumulative dose over time" are the variables that need to be considered. When you ask artificial intelligence it has little to do with how slowly you taper.

Artificial intelligence says:
"Here is why your adrenals might not have recovered fully despite a slow taper, and what you need to know:

5 mg is the "Critical Zone": Once you get below 5 mg, you are in the range where your adrenal glands are required to produce their own cortisol. If they are still "sleeping" (suppressed by the previous high doses), you will experience withdrawal symptoms, not because the taper was too fast, but because your body is not yet producing enough of its own cortisol.

Long-Term Suppression Takes Time: If you were on steroids for a long time (months or years), your adrenal glands can shrink (atrophy). It can take 6–12 months, and sometimes up to 18–24 months, for your HPA axis (hypothalamic-pituitary-adrenal axis) to fully recover."
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It just depends what you want to believe about how you feel. Symptoms are important but you need to know precisely what is causing the symptoms. You can't believe all pain is PMR and automatically increase your prednisone dose. People are too inclined to do that.

I know people promote the idea that tapering too quickly is the only problem we encounter. I can assure you that tapering too quickly was only part of a much bigger problem. The biggest part of the problem I had was long duration (12 years for PMR alone but "decades" for some other conditions) higher doses (over 20 mg most of the time) and a massive cumulative dose. Some of the conditions I had required 100 mg occasionally. PMR only needed 20 mg but most people have other conditions to contend with that also respond to Prednisone. It is false to think all pain that responds to Prednisone is "most likely" PMR pain.

My endocrinologist was surprised that I had a measurable cortisol level albeit low when I had a morning level checked. I was told to stay on 3 mg of prednisone until my cortisol level improved. I asked how long and the answer was "as long as it takes" but we will re-check another cortisol level again in 6 months. I was told not to taper at all for 6 months. Staying on 3 mg would have been impossible except that Actemra was controlling PMR while I stayed on 3 mg.

My cortisol level was only "adequate" for normal low stress days. Whether or not my adrenals could respond adequately to something stressful was was not certain.

My endocrinologist told me to call her if "anything happened" that was stressful. She added that I didn't need to call her first if I felt that I had to take Prednisone again but she still wanted me to inform her if I needed again "for any reason at all."

I had access to an emergency supply of prednisone.

I have inflammatory arthritis and PMR. Having both is possible and the symptoms overlap. I have a hard time knowing which condition is causing which pain. They can both flare up at the same time or independent of each other. When the inflammation is "systemic" anything can flare up.