Does anyone know how long it takes for a vitamin D deficiency to manifest? I just learned my DDIL is being tested for an as yet unknown illness. The doctor is thinking it may an auto-immune illness such as RA or lupus or lyme's disease, but it could be a deficiency from lack of sun. They've only been there 7 weeks; can the body be depleted that quickly? Most of what I could find talked about it being common in people who are lactose intolerant.