Key takeaways
- Vitamin D3 helps your body absorb calcium and contributes to normal bones, muscles and immune function.
- Vitamin K2 is needed to activate proteins involved in blood clotting and bone metabolism.
- Our capsule provides 125 mcg (5,000 IU) of D3 and 200 mcg of K2 as MK-7 per one-capsule serving.
- 125 mcg is above the 100 mcg (4,000 IU) daily upper limit set for adults in the US, so it's a product to discuss with your doctor, ideally alongside a blood test.
- If you take a blood thinner such as warfarin, don't start vitamin K without medical advice.
What each vitamin does
Vitamins D and K are both fat-soluble, which means they're absorbed along with dietary fat and can be stored in the body. That's where the similarity ends: they do different jobs.
Vitamin D3 (cholecalciferol)
Your skin makes vitamin D when it's exposed to UVB light, and you get small amounts from food: fatty fish like salmon and trout, egg yolks, UV-exposed mushrooms and fortified milk or cereals. D3 is the form your skin produces, and it's the form most supplements use.
Vitamin D's best-established role is helping the gut absorb calcium. It also contributes to normal muscle function and the normal function of the immune system. How much your skin makes varies a lot with season, latitude, time spent indoors, sunscreen use, skin tone and age, which is why people in short winter daylight often look at supplements.
Vitamin K2 (menaquinone-7)
Vitamin K comes in two main forms. K1 (phylloquinone) is found mostly in leafy greens. K2 (menaquinones) is found in fermented foods such as natto and some cheeses, and in smaller amounts in animal foods. Both are needed to activate proteins that control blood clotting, and proteins involved in bone metabolism.
MK-7 is one type of K2. It stays in the bloodstream longer than K1, which is one reason it's the form commonly chosen for supplements.
Why they're paired
The logic is simple. Vitamin D increases how much calcium you absorb, and vitamin K activates the proteins that help put calcium to use in bone. Pairing them in one capsule is a convenience: one product, one clear job, one step in your morning.
To be precise about the evidence: the pairing makes biological sense, but research is still working out how much the combination adds over each vitamin on its own. We'd rather say that plainly than overstate it.
Reading the label: mcg, IU and 5,000
Vitamin D is listed two ways on US labels: by weight in micrograms (mcg), and in International Units (IU). The conversion is fixed: 1 mcg of vitamin D equals 40 IU. So 125 mcg × 40 = 5,000 IU. Same amount, two units.
Here's how our capsule compares with the reference values used in the US:
| Reference | Vitamin D | Vitamin K |
|---|---|---|
| Our capsule (1 serving) | 125 mcg (5,000 IU) | 200 mcg (as MK-7) |
| Daily need, adults 19–70 | 15 mcg (600 IU) | 90 mcg women · 120 mcg men |
| Daily need, adults 71+ | 20 mcg (800 IU) | 90 mcg women · 120 mcg men |
| Upper limit, adults | 100 mcg (4,000 IU) | None established |
Daily need for vitamin D is the RDA; for vitamin K it is the Adequate Intake. Upper limit is the Tolerable Upper Intake Level. Values from the NIH Office of Dietary Supplements.
Two things are worth knowing. First, the upper limit is the most a healthy adult can take every day without medical supervision with little risk. It isn't a hard danger line, but 125 mcg sits above it. Higher-strength vitamin D is something doctors sometimes recommend after a blood test (the 25-hydroxyvitamin D test) shows low levels, so it's best treated as a conversation with your doctor, not a default.
Second, check what else you take. Many multivitamins and immune formulas, including our own Immune+, also contain vitamin D, and the amounts add up.
Who should talk to a doctor first
A vitamin D + K2 supplement isn't right for everyone. Check with your doctor or pharmacist before starting if any of these apply:
- You take a blood thinner such as warfarin. Vitamin K directly affects how these medicines work, and changing your intake can change your dose needs.
- You're pregnant or breastfeeding, or under 18.
- You have kidney disease, a condition that affects calcium levels, or a history of kidney stones.
- You take other medicines that interact with vitamin D, such as certain diuretics or steroids.
- You already take another product that contains vitamin D or vitamin K.
Too much vitamin D over time can raise blood calcium levels, which is why the dose matters and why more isn't automatically better.
How to fit it into your day
Take it with a meal
Because both vitamins are fat-soluble, many people take them with a meal that includes some fat, like eggs, yogurt or avocado toast. Always follow the directions on your bottle.
Anchor it to a habit
Consistency matters more than the exact hour. Keep the bottle where you have breakfast, and take it at the same point in your routine each day. One capsule a day means a 30-capsule bottle lasts about a month.
Food and daylight still count
A supplement fills a gap, it doesn't replace a varied diet. Fatty fish a couple of times a week, leafy greens, fermented foods and safe time outdoors all contribute.
The bottom line
Vitamin D3 and K2 do complementary jobs around calcium, and pairing them keeps a routine simple. Our capsule is a higher-strength option at 125 mcg of D3, above the general adult upper limit, so it's best used with your doctor's input, especially if you take medication. Read the label, count vitamin D from every product you take, and let a blood test guide the dose.
Sources
- Vitamin D: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements.
- Vitamin K: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements.
- Institute of Medicine (now the National Academies). Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press, 2011.
- Product information: the Vitamin D3 + K2 Supplement Facts panel, shown on the product page.
This article is general information, not medical advice. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.