Laura, you may remember that my daughter doesn’t even have a diagnosis yet. We are starting with a new endo and he is basically starting over with her testing. But she has been taking a low dose of prednisone prescribed by another dr, so he had her stop that for 2 days in order to do blood work. Well, because of her chronic hives, she had a flare up from suddenly stopping the pred. Her test results showed high cortisol and high aldosterone. I don’t really think the results can be trusted for accuracy because she’s been on steroids for over a yr. He also said her urine was "full of potassium and sodium."

But anyway, he ordered the 24 hr urine just to test for high aldosterone levels. She had to do salt loading for 3 days before, and then aldosterone levels in the urine are supposed to be low, which hers were. So she doesn’t really have high aldosterone levels (which I knew because it would have caused high BP whereas hers is always low).

I just found this out today: The random urine sodium test was supposed to be done right after the 24 hr collection to make sure that she had consumed enough sodium. However, no one in the lab saw that and they called me later to say that she needed another random urine test. It was actually done a week later. The sodium level after a salt-loading diet is supposed to be 200; hers was 190 on a normal diet! This is indicative of salt-wasting. The dr didn’t know this until I called today to let him know that the tests were not done the same day.

Anyway, to answer your question, the endo ordered the urine test as I explained above. I don’t know if he routinely orders a urine test or not, but I’ve read, as you guessed, that a urine test can be much more reliable but that they don’t usually do them because of the inconvenience of the collection. Certainly ask your dr about it. I’d be interested in what he says. And maybe ask a general question as to whether anyone else gets monitored that way.

P.S. This story really emphasizes why it’s important to look at the lab work. The endo had just told me it was normal because he didn’t know the tests weren’t done on the same day.