If you have tapering problems below 5 mg this might explain why.

Actually adrenal insufficiency symptoms are known to occur staring around 10mg, which happens to be what most people need their adrenal glands to provide daily. You have to remember that tapering 1mg at 10 mg is a 10% drop, tapering 1mg at 5mg is a 20% drop - you may not think that way but your body does and it is your body that counts, not your mind.

Hope 5 will turn it around, you’re not alone.

I'm not sure where the 10% rule comes from but I can never find any research that says this. I don't disagree with it but has this rule ever been investigated as part of a research study?

I think the important thing to know is the following: "A gradual reduction in prednisone dosage gives your adrenal glands time to resume their usual function. The longer you are on prednisone, the longer it will take to taper off. The amount of time it takes to taper off prednisone depends on the disease being treated, the dose and duration of use, and other medical considerations. A full recovery can take a week, months (or years.)"
https://www.mayoclinic.org/prednisone-withdrawal/expert-answers/faq-20057923
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Sometimes people become steroid dependent and need prednisone for the rest of their life. This condition is independent of PMR/GCA. It just depends on whether or not their adrenals recover along with other factors.

When I was able to stay on 3 mg of prednisone an endocrinologist said I shouldn't attempt to go any lower than 3 mg. My cortisol level was too low to safely taper any lower than 3 mg so that was the dose I stayed on for months. Being able to stay on 3 mg was only possible because a different medication that didn't suppress my adrenal function kept my PMR symptoms under control.

Many months later after my cortisol level improved the endocrinologist said there was no need for me taper from 3 mg to zero because my cortisol level was "adequate." I wanted more assurances that my cortisol level was adequate. The endocrinolgist said I would feel it if my cortisol level was too low again and then I should take more prednisone with her guidance. There was no way to predict what would happen when I discontinued prednisone simply because I took prednisone for more than 12 years.

There was no magic formula that says one way to taper off prednisone is any better than another way to discontinue prednisone. The only thing the endocrinologist cautioned me about was the possibility of an adrenal crisis. In that case, I was instructed to take prednisone again for any reason if I felt the need. There was no way of knowing if an adrenal crisis would happen. That hinged on whether a very stressful event occurred. My daily cortisol level was deemed to be adequate for normal days.

All in all, there are just too many factors that come into play. I have witnessed people with GCA tapered off Prednisone very quickly because of steroid psychosis. The patient absolutely refused to take her Prednisone so it didn't really matter how slowly she went. She came out of the psychosis and was more reasonable later on. She agreed to take her prednisone again but a much lower dose was needed.

DadCue, two points you make 'jump' out at me relating to me and the stage I am at in my course of treatment. They are: listening to my coach and the application of the 10% tapering rule. I seem to be 'under control' at 5 mg prednisone. At this point I have basically ruled out dmards and biologics. I'm attempting to taper to the lowest effective dose. My coach is discouraging splitting the 1 mg pills and suggesting alternating days with whole mgs. So I am for the second time alternating 5 and 4 mg. I haven't decided for how long yet before reducing to 4 mg. Being at 4 mg will be better than 5. Then I can attempt getting to 3 mg. Is tapering in whole mg amounts immunologically safer/as safe as tapering half mg amounts?
I'm assuming my coach/coaches were schooled in a tapering schedule with whole mg dosing because that's what has been suggested.
For whatever reason one of my Drs ordered an am cortisol, I'm taking 5 mg prednisone. The result was 7.1 ug/dl, normal range 4.8-19.5. I'm not sure what he was expecting, no comment from him yet. When you talk about 'too low' cortisol levels, are you meaning low normal or out of range too low?
If pmr appears to be inactive but you are symptomatic, either you have prednisone withdrawal, adrenal insuffiency, or something besides pmr is causing symptoms. It's a big dilemma.

I should add I have a consult/referral for PT to address the problems I'm having while tapering this time.

"The result was 7.1 ug/dl, normal range 4.8-19.5. I'm not sure what he was expecting, no comment from him yet. When you talk about 'too low' cortisol levels, are you meaning low normal or out of range too low?"
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I'm glad you said "normal range" because that is what it is. On days when your stress level is lower your adrenals might only need to produce 4.8. On stressful days your adrenals may need to produce 19.5 --- even this range isn't a fixed range. Some people do fine with less cortisol and others need a lot more. Your body needs to regulate this and it is impossible for us to do this by taking Prednisone. We can only do the best that we can depending on the circumstances.

Symptoms really matter here more than a cortisol level. You have to be able to distinguish between symptoms of adrenal insufficiency/prednisone withdrawal and PMR or whatever is being treated. At one stage it was said that I had inflammatory arthritis, PMR and secondary adrenal insufficiency caused by Prednisone. Sometimes it all was lumped together and called "systemic inflammation." I would just call it one big inflammatory mess.
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"If pmr appears to be inactive but you are symptomatic, either you have prednisone withdrawal, adrenal insuffiency, or something besides pmr is causing symptoms. It's a big dilemma."
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It doesn't have to one thing as in "either PMR /or" something else. I can easily be many things combined. It is a big dilemma and something I learned late in the game. It was very surprising to everyone involved when I was able to taper off Prednisone the first time. The focus was controlling PMR and maybe large vessel vasculitis and that was what Actemra was used for.

Almost as soon as I tapered off Prednisone the first time, I had a massive flare of uveitis while I was still on Actemra. My ophthalmologist restarted 60 mg of Prednisone again and switched my biologic. My ophthalmologist insisted that I be put on Humira instead of Actemra and said Humira was "optimal" for uveitis.

Humira may work for uveitis but it didn't work for PMR. As I tried to taper off Prednisone the second time, I couldn't go any less than 15 mg because PMR returned. My rheumatologist said it would be impossible to optimally treat everything.

My endocrinologist was clamoring for me to taper off Prednisone for fear that secondary adrenal insufficiency would recur.

My ophthalmologist wanted me to stay on Humira.

In the end ... we all had our say. However, I had the final say because my rheumatologist gave me the choice. I choose Actemra much to the chagrin of my ophthalmologist.

My endocrinologist was eventually happy. I was able to taper off Prednisone incredibly fast the second time after Actemra was restarted. This was even after being on Prednisone another year after I tapered off the first time. All my endocrinologist could say was that I had resilient adrenal glands and I was extremely lucky.

Just checking, can't you use a combination of 2.5 mg and 1 mg prednisone pills to taper by .5 mg?
A 2.5 and 2 1s would give you 4.5. I apologize if I'm missing something.

You 've certainly had more experience with prednisone than most of us. And I bet you've got a lot to teach us.

I was only prescribed 5 and 1 mg tablets. I need to be diplomatic about the dosing because when I originally asked about the half mg tapering I was told " I don't do that".
So next visit in a couple weeks I will don my 'diplomat hat' and approach the half mg taper again by asking for some 2.5 mg tablets. Thanks very much for the suggestion.

"Is tapering in whole mg amounts immunologically safer/as safe as tapering half mg amounts?"
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I personally don't think tapering by half mg amounts is necessary. I tried that too and it didn't make any difference. I agree with @jeff97 and just request the 2.5 mg and 1 mg tablets. Using those two tablets should allow you to do .5 mg increments except for 1.5 mg and .5 mg.

I have done it the way your rheumatolgist suggests too by doing 5 mg one day and 4 mg the next. Over 2 days, that averages 4.5 mg. That makes more sense to me if you want to prompt your adrenals to produce cortisol again. On the day you take the 4 mg dose that might give your adrenals a hint to make up the difference and produce some cortisol. I'm not sure if it works that way or not. I mostly say whatever works for you is all that matters.

I was flabbergasted when my endocrinolgist told me there was no need to taper from 3 mg to zero IF my cortisol level was adequate. It depended more on my cortisol level than my autoimmune disorders.

I think my endocrinologist consulted with my rheumatolgist to make sure I didn't need Prednisone to treat PMR. She also asked me I thought I needed Prednisone for PMR. I wasn't sure but Actemra seemed to have PMR under control.

Actemra wasn't intended to prevent uveitis from recurring. However, after some dose adjustments made easier with an infusion, of Actemra, it now seems like it can prevent flares of uveitis too.