Taking Vitamin D3 with K2 (MK-7) and Magnesium: how much did your 25(OH)D blood test actually go up after 12 weeks when taken with a fat-containing meal?
My winter 25-hydroxyvitamin D lab came back at 17 ng/mL (deficient), even though I was taking a dry 2,000 IU tablet with my black coffee in the morning! I learned two critical absorption rules here: first, Vitamin D3 is fat-soluble, so taking a dry tablet on an empty stomach wastes almost 35–50% of the dose; second, the liver and kidney enzymes that convert D3 into active calcitriol are 100% magnesium-dependent. I switched to an olive-oil softgel of 4,000 IU Vitamin D3 + 100 mcg Vitamin K2 (all-trans MK-7) taken right with dinner (salmon/avocado/olive oil), plus 200 mg elemental Magnesium Glycinate at night. My 12-week retest jumped from 17 ng/mL to 46 ng/mL while my serum calcium stayed right in the middle of normal! What daily dose and meal timing got your 25(OH)D into the 35–50 ng/mL sweet spot?
A clinical study in the Journal of Bone and Mineral Research (Dawson-Hughes et al., PMID 25441954) showed that taking Vitamin D3 with the largest fat-containing meal of the day increased serum 25(OH)D levels by an average of 50% compared to fasting intake. Note: Patients on Warfarin (Coumadin) must NOT take Vitamin K2 supplements, as K2 directly antagonizes warfarin anticoagulation.