How much skin pigmentation do you have?

People with highly pigmented skin do not make Vit D quickly with sun
exposure. They need longer exposure times.

Very light skinned people will make do with less time.

Where you live, you should have good exposure, and good levels. But you were on high dose Prednisone for 3 months and that drug does disrupt Vit D in the body. It is hard to say if you have recovered from that therapy yet.

You could use 2000 IU of D3 daily for a 3 mon period and retest to see what is going on. But you may not need the ultra high dosing that is given to some people with drastically low test results.

NOW brand makes its D3 in oil based gelcap...that is what I switched to.
I am unsure if dry tablets really deliver the D3 thru the GI tract. I used to use the dry form, but when I switched to the gel caps, I seem much much better somehow. (it may be something else, I don't know). I have not been tested yet. I tan very darkly in the summers and always feel good then. And typically get more pain, and worse in winters. This winter is the first for me with less pain. (I also take R-lipoic now, and benfotiamine however)