thank you for your post: you are very kind.
General multi's rarely contain adequate amounts of nutrients for health benefit, and where some are much better/worse than others.
At the risk of being sued by the manufacturers, Centrum are the lowest of the lowest in terms of quality and bio-availability. I remember one substantiated story of someones outside drains, leading from their downstairs toilet becoming blocked over a period of time: when this was investigated for clearance, the drain clearance specialists called in to clear this, found a huge accumulation of pills that lay as the root cause..........Centrum Multivitamins. They had passed through the digestive tract and expelled in the usual manner without being absorbed/changed whatsoever.!!!!
Your D-25 value is 6.6? Is that ng/ml or nmol/L ? Readings should ideally be 50 ng/ml or (125 nmol/L). Your reading of 6.6 means that you're severely deficient in Vitamin D3.
Personally I would not rely on any Internist/Cardiologist or whoever in reporting on your Vitamin D status, as in all probability they are ignorant of the Science behind it and the true levels you need for optimal/therapeutic health.
Since you have been taking some of your husbands Vitamin D in small doses, it might well be advisable to have your levels retested.
Ask your doctor for a 25-hydroxyvitamin D, or 25(OH)D, test. One may also refer to it simply as a “vitamin D test." In the past, doctors have been known to order a 1,25-dihydroxyvitamin D test. This is the wrong test as it cannot determine vitamin D deficiency. Make sure your doctor orders the correct test.
There are also nutritional cofactors needed when supplementing............. http://www.vitamindcouncil.org/about-vitamin-d/vitamin-d-cofactors/
I am sorry to hear that you are partially crippled and unable to get outside as much as you would like, but when you do, please avoid the heat of the Sun, and bask in the early morning and late afternoon sunlight to avoid the hives and headache. Heat being the main culprit here.
Kidney disease: you are best to seek out the opinion of a Doctor who is knowledgeable about supplementing with Vitamin D, as sometimes once a week doses of the Vitamin can be as high as 50,000ius over a few weeks to months to normalize blood levels. It also depends at what stage of progression your kidney disease is as to the dose.
In your situation I would try supplementing with 10,000ius per day for a couple of months, and then have your blood levels retested.