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

https://www.nadf.us/secondary-adrenal-insufficiency.html
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The following explains the challenges we need to overcome. I believe this is exactly what happened to me.

"The most difficult issue is that symptoms of adrenal insufficiency will be present during the tapering phase, because low levels of cortisol are the only trigger to the pituitary to stimulate the return of ACTH production and the restoration of normal pituitary-adrenal responsiveness.

The longer high dose steroids were given for a disease like asthma, rheumatoid arthritis, polymyalgia rheumatica or inflammatory bowel disease, the more likely that an individual will suffer from adrenal insufficiency symptoms on withdrawal of the steroids.

In addition, tapering off the steroids may cause a relapse of the disease that had been treated, causing a combination of disease symptoms overlapping with adrenal insufficiency symptoms. That is why it is very common for steroid tapers to be aborted, with a temporary return to therapeutic doses of glucocorticoids, followed by a slow attempt at tapering if the primary disease is in remission. "