D3 K2 Spray vs Tablets: What the Absorption Studies Found

A vitamin D3 and K2 spray and a tablet deliver the same nutrients, so the useful question is what studies found when the two formats were compared head to head.

Yes, for vitamin D the trials that compared the two found similar results. A winter crossover trial found an equal rise in blood vitamin D from a spray and from capsules.

A 2020 systematic review looked at all the randomized trials of a vitamin D3 spray against other formats. Three of the four found no difference between formats.

That is the honest comparison: a spray works as well as a tablet. It is a format choice, not an absorption trick. For more on how K2 fits in, see Do You Need K2 With D3?

It measured blood vitamin D, called 25(OH)D, after four weeks on each format. Blood 25(OH)D is the standard marker doctors use for vitamin D status.

Who took part: 22 healthy adults in Northern Ireland, tested in winter. Eighteen finished the study as planned.

Design: a crossover trial. Each person took the spray for four weeks and the capsules for four weeks, with a 10-week break between.

Daily amount used: 3000 IU (75 mcg) of vitamin D3 in both formats. The capsule arm used three 1000 IU capsules.

What changed: the average rise was 26.15 nmol/L with the spray and 30.38 nmol/L with capsules. The gap was not statistically significant (P = 0.313), and the authors called the spray an equally effective alternative.

The catch: the trial was short and small, it was open-label (everyone knew which format they took), and it studied healthy adults only. The spray was supplied by its maker.

The review concluded that a buccal spray, meaning one sprayed inside the cheek or mouth, "does not appear superior to the other modes of delivery." That wording appears in the 2020 Nutrients review.

What it covered: four randomized trials. They compared a spray with soft capsules in most cases and with oral drops in one.

Doses and length: 800 to 3,000 IU of vitamin D3 a day, for 30 days to 3 months.

What changed: one trial found the spray raised blood vitamin D more than capsules. The other three found no difference.

The catch: the trials were small and differed too much in design to be pooled.

So the studies support the spray as an equal option. They do not show it is absorbed better, and that is not the reason to choose one.

A tablet is counted in whole pieces, while a spray is measured in a volume of liquid, usually in milliliters (mL). The amount per spray differs from product to product.

You can see this in the trial above. The spray arm supplied the same 75 mcg a day that the capsule arm got from three capsules. A different spray may deliver a different amount per pump, so the Supplement Facts panel is the place to check.

Liquids can also be adjusted in smaller steps than a tablet can. That is a property of the format. How much vitamin D is right for you is a question for your doctor.

For reference, MedlinePlus lists^[4] the recommended daily amount of vitamin D for adults aged 19 to 70 as 600 IU (15 mcg). Its listed upper limit for adults is 4,000 IU (100 mcg).

For reference, our vitamin D3 + K2 spray has 55 mcg (2200 IU) of vitamin D3 and 100 mcg of vitamin K2 per 1 mL serving.

The trials did not measure preference, so no study says who likes which format. The differences are practical.

• A spray needs no water and no swallowing.
• A small bottle fits in a bag or desk drawer.
• Both vitamins can come in one oil, so there is one product to remember instead of two.

Both D and K are fat-soluble, meaning they dissolve in fat rather than water. When to Take Vitamins D and K covers timing with meals.

They work on the same job, which is moving calcium where the body needs it. Vitamin D helps the body absorb calcium^[4], which is needed for normal bone formation.* Vitamin K is a fat-soluble vitamin^[5] that the body needs for blood clotting, and some studies suggest it helps maintain strong bones in older adults.*

A 2024 review^[3] explains the link. Vitamin K is needed to activate osteocalcin and matrix Gla protein, two proteins that bind calcium. Vitamin D promotes osteocalcin production, and the review describes the two vitamins as acting in collaboration.*

What trials found: the same review cites a 2020 meta-analysis of eight randomized trials with 971 participants. Vitamin K given with vitamin D3 increased total bone mineral density.

The catch: the authors describe the evidence as somewhat limited and call for more research on the best intake ratio.

Takeaway: vitamins D and K work as a pair on calcium,* so a product that delivers both together makes practical sense. For the K2 form used, see Vitamin K2 as MK-4.

Vitamin K and vitamin D both interact with health conditions and medicines, so a doctor or pharmacist should be involved in the decision.

MedlinePlus notes^[5] that vitamin K can change how the blood thinner warfarin works. People on warfarin are told to keep their vitamin K intake steady from day to day. Too much vitamin D can raise blood calcium, and MedlinePlus lists^[4] kidney damage, kidney stones, nausea and confusion among the effects. It says toxicity almost always comes from supplements.

Check with your doctor first if you:

• take a blood thinner (anticoagulant) or any other medication
• are pregnant or breastfeeding
• are giving vitamins to a child
• have a kidney condition or a history of kidney stones
• have a health condition that affects calcium or vitamin D

The upper limit for adults is 4,000 IU (100 mcg) of vitamin D a day from all sources, according to MedlinePlus^[4]. A 25(OH)D blood test with your doctor shows your actual level.