We’ve used Carlson’s oil-based vitamin D gelcap in hundreds of patients and have seen consistent rises in blood vitamin D levels. Rises in blood 25-OH-vitamin D3 have been precisely what you’d expect with the stated 2000 unit per capsule dose, unlike many tablet forms of vitamin D that yield little or no rise in blood vitamin D3 levels. Carlson’s product has proven to be 100% tried-and-true for us, with virtually no side-effects whatsoever. It’s also reasonably priced. Capsules are small and easily swallowed, measuring about 1/4 the size of a standard fish oil capsule.