· By Kelin Marquet
How Much Vitamin D Should I Take?
Vitamin D — often called the “sunshine vitamin” — is essential for strong bones, a healthy immune system, and so much more. Yet, research shows around 42% of U.S. adults are deficient (even higher in some groups) (study).
So how much should you really take, and what’s the best way to get it? Let’s dig in.
What is Vitamin D?
Surprise — vitamin D is actually a hormone, not a vitamin. Your body makes it when skin is exposed to sunlight. Once produced, your liver and kidneys convert it into its active form.
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Helps regulate calcium and bone health.
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Plays a role in immune system support.
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Is fat-soluble, meaning your body can store it.
There are two forms in supplements:
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D2 (ergocalciferol)
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D3 (cholecalciferol) → shown to be 87% more potent than D2 and better at building long-term vitamin D stores (study).
You’ll find D3 in Why Not Natural’s Vitamin D3 + K2 liquid and capsules.
Why Is Vitamin D Deficiency So Common?
Even if you spend time outdoors, low levels are common. Reasons include:
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Indoor lifestyles and sunscreen use.
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Living far from the equator.
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Age-related decline in kidney activation.
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Digestive issues (Crohn’s, celiac) that impair absorption.
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Higher body weight (linked to lower vitamin D status).
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Low intake of cofactors like vitamin K, magnesium, and zinc.
How Much Vitamin D Should You Take?
The NIH recommends (factsheet):
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Babies: 400 IU / 10 mcg daily
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Children & adults up to age 70: 600 IU / 15 mcg daily
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Adults 70+: 800 IU / 20 mcg daily
But research suggests higher amounts may sometimes be needed to raise blood levels:
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3,800–5,000 IU/day maintained healthy vitamin D status in one trial (study).
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Long-term hospitalized patients tolerated 5,000–50,000 IU/day under supervision, with no reported adverse effects (study).
Translation: individual needs vary a lot. Always check with your doctor before exceeding the NIH daily values.
How Much Vitamin D Should You Take?
The NIH recommends (factsheet):
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Babies: 400 IU / 10 mcg daily
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Children & adults up to age 70: 600 IU / 15 mcg daily
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Adults 70+: 800 IU / 20 mcg daily
But research suggests higher amounts may sometimes be needed to raise blood levels:
-
3,800–5,000 IU/day maintained healthy vitamin D status in one trial (study).
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Long-term hospitalized patients tolerated 5,000–50,000 IU/day under supervision, with no reported adverse effects (study).
Translation: individual needs vary a lot. Always check with your doctor before exceeding the NIH daily values.
Best Ways to Get Vitamin D
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Sunlight: midday sun is most effective, but limited by geography, lifestyle, and skin tone.
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Food: cod liver oil and fatty fish are classic sources.
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Supplements: a convenient option! Why Not Natural’s Vitamin D3 + K2 liquid and capsules.
Daily vs. Weekly vs. Monthly Dosing
Because vitamin D is fat-soluble, it can be stored in the body. This led to the idea of weekly or even monthly dosing.
However, studies show daily intake is more effective at maintaining stable vitamin D status than weekly or monthly doses, even when the totals are equal (study).
Best practice: take vitamin D regularly, ideally every day.
Conclusion
Vitamin D is critical for bone health, immunity, and more. Sunlight and food sources help, but for many people, supplementation is the most reliable way to meet needs.
If you’re looking for an easy option, check out Why Not Natural’s Vitamin D3 + K2 liquid and capsules.
Disclaimer: This article is for educational purposes only and is not medical advice. Please consult your healthcare provider before starting or changing any supplement routine.
References
(1) Prevalence and correlates of vitamin D deficiency in US adults
https://pubmed.ncbi.nlm.nih.gov/21310306/