Vitamin D helps your body absorb calcium from food and supplements. That sounds straightforwardly positive, but there is a catch. Absorbed calcium needs to be directed to the right place, which is your bones and teeth. Without adequate vitamin K2, that calcium can end up depositing in your arteries and soft tissues instead, which is the opposite of what you want.
K2, specifically in the MK-7 form that Thorne uses, activates the proteins that direct calcium to the bones and keep it out of the arteries. Combining D3 and K2 means you get the full calcium-absorbing benefit of vitamin D with the proper routing that K2 provides. They work together, and taking D3 without K2 misses half the picture.
Vitamin D deficiency is genuinely widespread. Studies estimate that somewhere between 40 and 70 percent of Americans are deficient or insufficient. The consequences are significant and include weakened immune function, poor bone density, reduced muscle function, lower mood, and impaired sleep quality. Getting vitamin D levels right matters for almost every system in the body.
Most people who live in northern latitudes, work indoors, or use sunscreen consistently cannot get adequate vitamin D from sun exposure alone. Supplementation is not optional for most of us, it is a necessity.
Vitamin D is a fat-soluble vitamin, which means it absorbs best when taken with fat. Thorne's liquid format suspends the vitamins in a medium chain triglyceride oil base, which means the fat needed for absorption is already built into the delivery mechanism. You do not need to time it with a meal that contains fat. The liquid also allows for more flexible dosing, which is useful if you want to adjust your intake based on blood testing results.
Thorne is one of the most trusted names in the supplement industry for a reason. Their manufacturing standards exceed what is required by law, they do not use unnecessary additives or fillers, and they test their products rigorously. For a fat-soluble vitamin like D3 where dosing accuracy matters, that level of quality control is especially important.
If you are going to supplement with vitamin D, I strongly encourage getting your 25-OH vitamin D levels tested before you start and after a few months of supplementation. It is a simple blood test and knowing your actual level allows you to dial in the right dose rather than guessing. Most people do well with a target of 50 to 70 ng/mL.
| Vitamin D3 per Serving | 1000 IU (adjustable) |
| Vitamin K2 (MK-7) | 200mcg |
| Format | Liquid drops |
| Base | MCT oil |
| Servings | 600 |
| Artificial Additives | None |
| Price per Serving | ~$0.06 |
| NSF Certified | Yes |