How Much Vitamin D is Too Much?

How Much Vitamin D is Too Much?

You’ll never absorb too much vitamin D from the sun.

That’s because the darker you become, the less vitamin D you absorb. There is also not enough vitamin D that naturally occurs in food to ever pose a problem. Because we are not in the sun as much as our forefathers were, Vitamin D deficiency is a big problem but taking too much vitamin D in supplement form can be unhealthy at high doses.

When using Vitamin D at dosages higher than 4000 IU per day, it’s recommended that you consult with a doctor or a naturopathic doctor.

The NIH has determined that the upper tolerable limit to be 4000 IU per day. Higher doses may be okay for you but it is advised that you never take more than 4000 IU per day without doctor supervision. Read more to find out why.

I especially wanted to write about Vitamin D because there are more people taking high doses right now because they think it might boost their immune system. I won’t be talking about whether or not taking Vitamin D supports your immune system against you know what because we know so little about the virus and how supplements interact with it. But if you are taking Vitamin D right now, I want you to have the facts because I care about your long term health.

So how exactly is Vitamin D not safe at higher dosages?

One word: Toxicity!

Two words: Bone loss.

Another 2 words: Kidney stones.

Toxicity can occur at super mega doses for long periods of time which I have never ever recommended.

“Taking 60,000 international units (IU) a day of vitamin D for several months has been shown to cause toxicity.” This does not mean you can take 55,000 IU per day for several months! Never take more than 4000 IU per day without consulting with a doctor or naturopathic doctor.

But doesn’t Vitamin D protect against bone loss? Yes, but some recent studies have suggested that high doses of Vitamin D, anything above 400 IU, may be associated with bone loss. What?! 400 IU?! That’s less than the RDA of 600 IU per day. So, more studies are needed and that’s exactly what they say.

Kidney stones can be formed if high dose D causes calcium loss from the bones.

Ouch! Ask your doctor or naturopathic doctor to test your Vitamin D and calcium levels. I especially like to test both 25 OH Vitamin D (most commonly tested) and 1,25-dihydroxyvitamin D. The latter is an indicator of kidney stone formation. Some people will never have optimal levels of 25 OH Vitamin D because they are so good at producing 1,25-dihydroxyvitamin D…which happens to be the active form of Vitamin D.

So, should you stop taking Vitamin D?

It depends. Do you have issues with absorption? Have you had your Vitamin D tested? The established optimal range is 40-80. Are you taking high doses for long periods of time? Has your blood calcium been tested? This is why asking your doctor, or naturopathic doctor, for guidance is a good idea.

Should you take Vitamin K and Calcium supplements with Vitamin D?

High dose Calcium and D together have been shown to increase the risk of calcium deposits in the arteries which causes cardiovascular disease. This is because D can pull Calcium out of the bones, and with the addition of Calcium supplements…it’s just too much Calcium!

Vitamin K keeps Calcium in the bones.

Talk to your doctor! Fun fact: Green, leafy vegetables contain a lot of K! In fact, they contain so much that doctors usually prescribe no green leafy vegetables to their patients on the medication Warfarin (K and Warfarin are not a good combo!). Anyway, just ½ cup of kale contains over 500 mcg of Vitamin K. Woot! Woot! Yeah!

The facts:

Vitamin D is my favorite! Okay, that’s probably not a fact that you really needed but I’ll tell you why: Colorectal cancer.

What does Vitamin D have to do with colon cancer?

A lot! According to a study by the National Academy of Medicine, it was found that low serum Vitamin D levels were associated with a 31% higher risk of colorectal cancer. I’ll take that! Colorectal cancer runs in my family.

Some studies have also found that patients with colon cancer fare better when given high doses of Vitamin D. A lot of this has to do with a certain gene controlling VDR (Vitamin D receptor). The absence of VDR or dysfunction in the gene leads to dysbiosis and susceptibility to colon cancer. It’s been found that Vitamin D regulates antitumor immunity in colorectal cancer.

So, how does high dose Vitamin D help prevent or treat colorectal cancer if the gene is not working? Well, there’s a lot of copies of the VDR gene, some work and some don’t. By flooding it with large doses of Vitamin D, it provides enough D for the receptors that are working properly. That’s the theory I was taught! Time will tell if it’s true. There is still so much to learn especially in genetic medicine.

Vitamin D can help improve: “…resistance to chronic diseases (such as cancer and cardiovascular diseases), physiological parameters (such as immune response or levels of parathyroid hormone), and functional measures (such as skeletal health and physical performance and falls).” I quote the NIH.

It’s used in chronic fatigue/post viral syndrome, colds, and flus but studies are weak to prove efficacy.

Vitamin D may improve muscle strength. Most of us could use that.

It’s used in psoriasis (ask a dermatologist).

4000 IU is considered a tolerable upper limit dose.

If you are taking greater than 4000 IU, please so only under the supervision of your doctor or naturopathic doctor.

Want to learn more about Vitamin D and how much you should take? Schedule your free phone consultation HERE.

Dr. Kimberly Brown, ND sees patients remotely and in office. She has many years of experience working with hormone imbalances. She can evaluate your adrenal, thyroid, sex hormone health along with mulit nutrient analysis, food intoleance, and gastrointestinal health. Call us at 408-357-3422 or email at