No, and none of the clinicians I've seen have any idea what's going on. They just know I've been tested 6 times and my levels haven't moved to acceptable levels even as I've been on supplements pretty regularly. I've experimented here and there - like the 3 weeks of hiking and being off supplements and while I was outside a bunch last summer - but it seems either I'm not making or I'm not storing. They could do more invasive tests - like a biopsy from my intestine - but I feel so good on the supplements, I don't see any reason to change anything. My nutritionist thinks my levels will bounce back after sticking with the supplements and I think that's the best course of action.