Vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) are both forms of vitamin D, but D3 is generally considered more effective at raising and maintaining vitamin D levels in the blood. Vitamin K2 is a different nutrient altogether, part of the vitamin K family, and some people take it alongside vitamin D because the two nutrients both play a role in how the body uses calcium.
This article looks at what separates D2 from D3, where K2 fits into the picture, and what to check on a label if you are choosing a supplement. We cover the specific dose you need through a Canadian winter in a separate guide.
What is the difference between D2 and D3?
Vitamin D2 and D3 are both converted by the liver and kidneys into the active form of vitamin D that the body actually uses. The starting materials are different, though. D2 comes from plant and fungal sources, such as UV-treated mushrooms or yeast, while D3 is made from animal sources like lanolin from sheep's wool, or from lichen for a plant-based option.
Both forms support the same basic jobs in the body, including helping the body absorb calcium and supporting normal muscle and immune function. The practical difference shows up in how well each form raises and holds blood levels over time, which is why D3 is the form used in most Canadian supplements.
Why D3 is usually the better choice
D3 is generally considered more effective than D2 at raising and maintaining vitamin D levels in the blood. This is one reason most vitamin D supplements sold in Canada, including fortified foods, use the D3 form.
D2 is still a legitimate option, and it is useful for people who want a strictly plant-based supplement without lichen-derived D3. If you choose D2, you may need to check the label more carefully and consider checking your levels with a doctor to make sure it is doing the job you expect.
Where does vitamin K2 fit in?
Vitamin K is a separate vitamin from vitamin D, and it comes in two main forms: K1 (phylloquinone), found mostly in leafy green vegetables, and K2 (menaquinone), found in some fermented foods and animal products. Vitamin K is needed for normal blood clotting, and it also plays a role in bone health.
Vitamin D helps the body absorb calcium from food, while vitamin K supports the proteins involved in directing that calcium appropriately in the body. Because of this connection, some supplements combine vitamin D3 with K2, and some people choose to take them together. The two nutrients do different jobs, so neither one replaces the other.
D2, D3, and K2 at a glance
Here is a quick comparison to keep the three apart when you are reading labels.
| Nutrient | Typical source | Main role |
|---|---|---|
| Vitamin D2 | Plants, fungi, yeast | Helps the body absorb calcium; supports immune and muscle function |
| Vitamin D3 | Animal-derived (lanolin) or lichen | Same roles as D2, generally raises and maintains blood levels more effectively |
| Vitamin K2 | Fermented foods, some animal products | Supports normal blood clotting; involved in how the body directs calcium |
What to look for on a label
If you are comparing products, a few details make the choice easier.
- Check whether the form is labelled D3 (cholecalciferol) or D2 (ergocalciferol).
- Look for a lichen-based D3 if you want a plant-based option instead of D2.
- If a product combines D3 and K2, check that the vitamin K amount is reasonable and note the form of K2 listed (menaquinone-7 is common).
- Look for an eight-digit Natural Product Number (NPN) on the label, which means Health Canada has reviewed the product for safety and label accuracy.
- Note the amount per dose in IU or mcg so you can compare it with the daily reference values.
Safety notes for vitamin D and K2
Adults aged 19 to 70 need 600 IU (15 mcg) of vitamin D per day, rising to 800 IU (20 mcg) after age 70; the tolerable upper intake level from all sources is 4,000 IU (100 mcg) per day. Going well above this level over time is not advised without a doctor's guidance.
Vitamin K has an adequate intake of 120 mcg per day for men and 90 mcg for women, and no upper limit has been set. However, vitamin K can interact with blood-thinning medications such as warfarin, since it plays a role in clotting. Anyone taking warfarin or other blood thinners should talk to a doctor or pharmacist before adding a vitamin K2 supplement, or before making large changes to how much vitamin K-rich food they eat.
Pregnant or breastfeeding people, and anyone managing kidney disease or taking calcium or heart medications, should also check with a healthcare provider before combining vitamin D and K2 supplements.
The short version
- D3 (cholecalciferol) and D2 (ergocalciferol) both support vitamin D status, but D3 is generally more effective at raising and maintaining blood levels.
- D3 comes from animal sources or lichen; D2 comes from plant and fungal sources.
- Vitamin K2 is a separate nutrient from vitamin D and supports normal blood clotting and calcium handling in the body.
- Some supplements combine D3 and K2, but each nutrient still has its own distinct role.
- Vitamin K can interact with blood thinners like warfarin, so check with a pharmacist before adding it if you take that medication.
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Frequently asked questions
Is vitamin D3 always better than D2?
D3 is generally considered more effective at raising and maintaining vitamin D levels in the blood, which is why it is the more common form in Canadian supplements. D2 can still be a reasonable choice, particularly for people avoiding animal-derived ingredients and not using a lichen-based D3.
Do I need to take vitamin K2 with vitamin D?
No, they are separate nutrients with different jobs, and vitamin D works on its own without K2. Some people choose combination products because both nutrients relate to calcium in the body, but it is a personal choice rather than a requirement.
Can vitamin K2 replace vitamin K1?
K1 and K2 are both forms of vitamin K and contribute toward the same daily adequate intake, but most people get K1 from leafy greens and K2 in smaller amounts from fermented and animal foods. Neither form needs to be excluded if you are eating a varied diet.
Is it safe to take vitamin K2 if I am on blood thinners?
Vitamin K plays a role in blood clotting, so it can interact with medications like warfarin. Talk to your doctor or pharmacist before starting a K2 supplement if you take a blood-thinning medication.
Keep reading
- Everyday Immune Support: Vitamin C, Zinc, Vitamin D and Elderberry
- Vitamin D in Canadian Winter: How Much From October to April
- Zinc Forms, Doses and Why It Can Upset Your Stomach
- Elderberry and Echinacea: What the Research Actually Shows
Sources
- NIH Office of Dietary Supplements: Vitamin D
- NIH Office of Dietary Supplements: Vitamin K
- Health Canada: Reference values for vitamins
- Health Canada: Licensed Natural Health Products Database
This article is for general information only and is not medical advice. Talk to your doctor or pharmacist before starting a supplement, especially if you are pregnant or breastfeeding, take medication, or have a health condition.