Vitamins D3 and K2 are widely recognized as a powerful combination that supports bone strength, calcium absorption, and immune health. Vitamin D3 helps your body absorb calcium, while vitamin K2 ensures that calcium is directed to where it's needed — your bones and teeth — and not to your arteries.
Keep reading to find out the optimal daily dosage of vitamins D3 and K2 for maximum health benefits!
Vitamin D
Vitamin D is a fat-soluble vitamin that can be ingested by foods such as dairy products, fatty fish, and eggs, but is mainly synthesized by the human skin when exposed to sunlight (1).
Vitamin D helps regulate the amount of calcium and phosphate in the body. These nutrients are essential for maintaining the health of bones, teeth, and muscles.
Vitamin D:
- promotes calcium absorption,
- regulates bone growth,
- strengthens the immune system.
Between late March or early April to the end of September, most people can make all the vitamin D they need through sunlight on their skin and from a balanced diet.
During the autumn and winter, you need to get vitamin D from your diet or supplements because the sun is not strong enough for the body to make vitamin D.
A deficiency in vitamin D can lead to bone deformities such as rickets in children, and in adults, it can cause osteomalacia — a condition in which bones become soft and weak, increasing the risk of pain and fractures.
Vitamin K
Vitamin K is a fat-soluble vitamin that:
- helps your blood clot,
- aids in wound healing,
- may help keep your bones healthy.
Vitamin K refers to a group of related fat-soluble vitamins. Vitamin K includes vitamin K1 (also called phylloquinone), as well as vitamin K2 (menaquinone). They work differently in your body and come from different food sources.
Vitamin K1 is primarily found in plant-based sources such as green leafy greens and blueberries, whereas vitamin K2 is more commonly present in animal products, fermented foods, and certain types of cheese. Vitamin K2 can also be produced by gut bacteria.
Vitamin K2 is absorbed by your body more slowly than vitamin K1. Whereas vitamin K1 is quickly filtered out of your blood, often within a matter of hours, vitamin K2 has the potential to be longer-lasting. That means it stays in your body longer — several days even — and has more time to do its good work.
Vitamin D – normal range
The normal range of 25-hydroxyvitamin D, also known as a 25(OH)D, is measured as nanograms per milliliter (ng/mL) or nanomoles/liter (nmol/L).
Many experts recommend keeping 25(OH)D levels between 20 and 40 ng/mL (equivalent to 60–100 nmol/L) for general health. Some specialists suggest a slightly higher range of 30 to 50 ng/mL (or 75–125 nmol/L) as optimal.
You’re generally considered vitamin D deficient if your 25(OH)D level falls below 30 ng/mL (75 nmol/L), while levels under 12 ng/mL (30 nmol/L) are classified as severely deficient, potentially leading to bone-related conditions such as osteomalacia in adults or rickets in children.
You can get your blood tested and — if your provider thinks you need it — start taking vitamin D3 supplements. You should see your provider every three months until you reach steady vitamin D blood levels (that usually takes three to six months).
Vitamin D – dosage per day
The Recommended Daily Allowance (RDA) for vitamin D is determined by age, biological sex, and whether or not you’re pregnant or lactating, but the National Institutes of Health (NIH) recommends everybody get somewhere between 400 and 800 international units (IU) of vitamin D per day.
The RDA for vitamin D is 15 micrograms (600 IU) for both men and women aged 1 to 70 years, and increases to 20 micrograms (800 IU) for those over 70. The RDA for pregnant and lactating women remains at 15 micrograms (600 IU).
How much vitamin D a person should take depends on how significant their deficiency is. In cases of severe vitamin D deficiency, your provider may prescribe a short-term course of very high-dose pills or injections.
If your vitamin D levels are less-than-ideal, but aren’t below the 30 ng/mL mark, they’ll likely suggest you take an over-the-counter vitamin D3 supplement.
If you’re experiencing specific symptoms like depression, your provider may encourage you to take up to 4,000 IU of vitamin D per day.
How much vitamin D is too much?
Vitamin D blood levels become a problem when they approach 100 ng/mL. And it’s only possible to exceed 100 ng/mL by over-supplementation.
If you have too much vitamin D in your blood, it will cause extra calcium absorption. This can lead to symptoms like muscle pain, mood disorders, abdominal pain, frequent urination, and kidney stones.
Do not take more than 100 micrograms (4,000 IU) of vitamin D a day, as it could be harmful. This applies to adults, including pregnant and breastfeeding women and the elderly, and children aged 11 to 17 years. Consuming more than this is not advised unless prescribed by a healthcare professional.
Vitamin K – dosage per day
The recommended daily dosage of vitamin K depends on age, sex, and specific health conditions.
According to the National Institutes of Health (NIH), there is no established Recommended Dietary Allowance (RDA) for vitamin K. Instead, the NIH provides Adequate Intake (AI) values, because there is not enough evidence to develop an RDA.
For adult males aged 19 and older, the AI is 120 micrograms per day, for adult females aged 19 and older it is 90 micrograms per day, and for pregnant and lactating women, the AI is also 90 micrograms per day. For children and adolescents, the dosage ranges from 30 – 75 mcg per day, depending on age.
Unlike vitamin D, most people get all the vitamin K they need by eating a varied and balanced diet. Any extra vitamin K you get is stored in your liver, so it’s fairly rare to be vitamin K deficient.
How much vitamin K is too much?
The AI for men and women is 120 and 90 micrograms per day, respectively. No adverse effect has been reported for individuals consuming higher amounts of vitamin K, so a Tolerable Upper Intake Level (UL) was not established.
What to know before taking vitamins D3 and K2
Before starting any new supplement regimen, including vitamin D3 and K2, it’s important to consult your healthcare provider — especially if you are pregnant, breastfeeding, taking medications, or managing a medical condition.
If you are on blood-thinning medication, speak with your doctor before increasing your intake of vitamin K1 or K2, as these vitamins can affect blood clotting.
Literature sources:
- van Ballegooijen AJ, Pilz S, Tomaschitz A, Grübler MR, Verheyen N. The synergistic interplay between vitamins D and K for bone and cardiovascular health: a narrative review. Int J Endocrinol. 2017;2017:7454376. doi:10.1155/2017/7454376. PMID: 29138634; PMCID: PMC5613455.
