Supplement Series: How Much Vitamin D You Should Be Taking

When people think of vitamin D they generally think it does one thing – build bones. It turns out it does much, much more. Vitamin D controls over 1000 processes in your body. When you are completely deficient, you end up with dysregulation of mineralization in your bones called rickets. When you’re not at optimal levels, you miss out on many more things that could help you perform at a much higher level. It turns out that a lot of people won’t be at optimal levels naturally due to lifestyle, so that leaves: supplementation. How much vitamin d do you take though?

Why You Need OPTIMAL Levels

Vitamin D isn’t even really a vitamin, it more so acts like a hormone throughout the body. Hormones regulate critical pathways that promote health and have a cascading effect throughout the rest of the body. Without an optimal level of vitamin D, you miss out on several extremely important processes in your body. This includes regulating immunity, decreasing type II diabetes, decreasing cancer rates, decreasing dementia, increasing fertility and positive sex hormones, improving gut function and decreasing overall inflammation.

Telomere length for longevity

Vitamin D can also help prevent aging by reducing the shortening of telomeres. Telomeres are the caps on the long strands of your DNA that prevent aging. Think of the ends of your shoe laces that have those little plastic caps. These generally shorten when cells divide. When measured, telomeres are a direct sign of cell aging. The shorter your telomeres, the older your cellular age. Vitamin D has been found to protect against DNA damage and prevent cellular aging by protecting the lengths of your telomeres. 

Are you deficient or insufficient?

Over 75% of Americans are deficient in vitamin D. This figure is probably much higher after accounting for those who are not technically deficient, but are still not at an optimal level. In our magnesium and performance article, we explained that RDIs are often much lower than ideal.

Just because there is an established amount when your doctor tests that is “deficient” or out of range, doesn’t mean that there isn’t an “optimal” range where your body thrives. Just because you didn’t cross an imaginary line of sickness doesn’t mean you shouldn’t care about your levels and the trend line of those levels.

With respect to vitamin D, minimums are established to protect bone mineralization, but not to help regulate 1000 other bodily functions. An estimate of up to 95% of people are not in an optimal range of vitamin D. This means that up to 95% of Americans are missing out on the myriad of genes and processes that vitamin D regulates and improves. So, that leaves supplementing, but how much vitamin D should you take?

A fat soluble vitamin

Vitamin D is a fat soluble vitamin. This means a few different things. If you take supplemental vitamin D, do so with fat. Without fat, the bioavailability is decreased, rendering the supplement useless to your body. 

This also means if you are overweight, you are going to need a higher dose than those who don’t carry as much body fat. The fat solubility will concentrate in your adipose tissue and will never get to the end organs and glandular tissues to make positive changes in your body.

This means it generally you should be taking vitamin D with food, if you have meals that contain fat. However, some forms of vitamin D supplementation already contain some fats (fish oil, coconut oil, etc).

Should you supplement?

The easiest way to figure out if you should be supplementing – get some bloodwork done. Test, don’t guess. Many people will get their bloodwork back and it will not be deficient, so their doctor will never say anything to them about what to do. However this is far from the optimal. Anything under 25 ng/mL is technical deficiency, yet very far from what an optimal level would be. Optimal levels for serum vitamin D levels are at a much higher 65-75 ng/mL.

Vitamin D synthesis from the sun is widely variant. The darker skinned you are, the lower the rate of vitamin D synthesis you will have. Season, proximity to the equator, clothing, and sunscreen can all modify the synthesis of vitamin D as well.

If you’re like a typical American who sits inside most of the day then goes home after work and sits inside until the sun sets, you should probably supplement. If you’re an athlete looking to take full use of recovery and reduction of inflammation, then most likely. If you’re a light skinned individual who works an outdoor job near the equator, then you can probably skip supplementing.

WHICH form of Vitamin D is best?

There are many different types of vitamin D you can take, and I can sit and bore you with the chemical compounds all day, or I can just say simply “D3”. Vitamin D3 is the form that converts the best in the body, and is the one you should be supplementing with if you choose to supplement.

How much Vitamin D Should You take?

So how much vitamin D should you take? Look for roughly 1000-1500 IU per 25 pounds of body weight. If you have more fat mass, take a little more. Look towards supplementing in the morning as sometimes vitamin D can be stimulatory. And remember, supplementing with fat is key. 

As you can see, supplementing with vitamin D is probably a good idea for most people. Most people don’t take enough as the RDI is far too low. Drawing your blood is the only way to definitely know how much or if you need to supplement. Like mentioned above, you should be testing your blood on a regular basis and vitamin D should be one of the values you look for.

However, you should be keeping an eye on this. Because vitamin D is fat soluble, this means that you can actually take TOO much. It can accumulate in your tissues unlike some other vitamins, so more is NOT always better. If you’re testing above 75 ng/mL, back off the supplementation. That being said, if you’re going to be traveling for a little bit, you can supplement ahead of time. Triple or quadruple your dose for a few days and it will be stored metabolize over time.


  • Vitamin D Controls over 1000 processes in your body

  • 75% of Americans are deficient

  • Shoot for between 65-75 ng/mL — test, don’t guess

  • How much vitamin d? Take 1000-1500IU/25 lbs

  • Take vitamin d3, with fat

Now you know how much vitamin D to take, when, and how to test if you’ve taken enough, time to go grab some and get healthy! You can double up with some cod liver oil, which already has some naturally occurring vitamin D, or get some with some fat already in it.