Vitamin D3 vs Vitamin D2
Are You Getting the Right One?

Vitamin D3, Vitamin D2. They’re the same thing right? Well, no. Disease prevention from Vitamin D is very much affected by which type of Vitamin D that you are taking. Vitamin D comes in two different formulations. Vitamin D2, also called ergocalciferol; and Vitamin D 3, also called cholecalciferol.

Vitamin D2 was the first synthetic form of Vitamin D and is the form of vitamin D in almost all Vegan Vitamin D supplements. It was used, and still is in many cases, to fortify foods, make some Vitamin D supplements and is the basis for ALL Prescription Vitamin D. Many over the counter Vitamin D supplements and ALL prescription Vitamin D supplements contain Vitamin D2. So what's the difference? Vitamin D is Vitamin D, right? And a PRESCRIPTION is going to provide a form with the best Vitamin D absorption and the best quality, right? Unfortunately, no. 



But it is a far inferior form of Vitamin D that does not get absorbed into the body well. This is a phenomenon called bioavailability- or in this case simply Vitamin D Absorption. Many vitamins are not necessarily bioavailable, therefore taking vitamins does not mean that you actually ABSORB the vitamin.

Vitamin D2 is one of these vitamins that is not very bioavailable, yet this is the ONLY form used in the Vitamin D 50,000 IU pills that you will get from EVERY pharmacy!! The Vitamin D Research supports this extremely well:

  • “… cholecalciferol (vitamin D 3) is substantially more potent than ergocalciferol (vitamin D2).” ‘Vitamin D in Health and Disease’ Heaney, RP
  • “Vitamin D2 should not be regarded anymore as suitable for supplementation or fortification.” From ‘Vitamin D2 or vitamin D3?’ Mistretta, VI et al
  • “D2 (ergocalciferol) has lower bioactivity, poorer stability, and shorter duration of action, resulting in approximately 33% lower potency compared with vitamin D3” From ‘The Value of Vitamin D3 over Vitamin D2 in Older Persons’ Barbara J. Zarowitz PharmD, FCCP, BCPS, CGP, FASCP



  • “Vitamin D2, or ergocalciferol, should not be regarded as a nutrient suitable for supplementation or fortification.” From ‘The case against ergocalciferol (vitamin D2) as a vitamin supplement’. Houghton LA, Vieth R.
  • "...Vitamin D2 is only about 20-40% as effective as cholecalciferol …” Michael F. Holick, ‘The Vitamin D Epidemic and its Health Consequences’.

Vitamin D3- Not Just Absorption

If it were simply an issue of Vitamin D Absorption, then you could simply take more to do the same job. But unfortunately, vitamin D 2 just doesn't DO the job that vitamin D is Supposed to do.

One consequence of vitamin D deficiency is that the Parathyroid Gland becomes overactive, altering calcium metabolism. When vitamin D is replenished, then parathyroid hormone is lowered back to normal levels. But in a few studies, the parathyroid hormone was NOT decreased to normal with the administration of vitamin d2, but it DID decrease to normal with the Vitamin D3!

You can see that Vitamin D Absorption and effectiveness is dependent upon which type of Vitamin D you choose, and that it’s a no-brainer to choose the right form of Vitamin D supplement.



If you choose to do Vitamin D Therapy , don't bother getting a"Prescription Strength" Vitamin D supplement, just go Buy Yourself a Bottle of Vitamin D 3 instead. 

Make sure that it says Vitamin D 3 or cholecalciferol.

Even better, if you want to avoid Vitamin D Side Effects, get the full Vitamin D Absorption Pack we've designed as a result of the many side effects that people experience from not taking vitamin d the 'smart' way. But aren't Vitamin D 3 supplements dangerous? Can't you Overdose on Vitamin D? There is a risk to everything that you do. So, of course there is a risk with taking Vitamin D 3 supplements.

But.... click next find out the truth.

Next --->
Overdose on Vitamin D

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Vitamin D Resources


Frequently Asked Questions
About Vitamin D

How do I do
Vitamin D Therapy
What About Vitamin D Toxicity?
What are Vitamin D Facts? What are the
Causes of Vitamin D Deficiency?
Why Shouldn't I Take
Prescription Vitamin D?
What are some of the
Vitamin D Foods?


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I Can't Find Just Plain Vitamin D 
Is there a Vitamin D available by itself, or does it only come in D2 or D3? I was told that I should get just plain Vitamin D, but I can't find it unless …

Why is Vitamin D2 All that the Doctors Prescribe? 
Is vitamin d2 all the doctors prescribe? What is the reason for that?I have celiac disease and my vitamin d is low, what all should I be doing since my …

Taking Vitamin D2 and D3 
I was perscribed D2 for low level Vitamin D. It was at 8. I was given 50,000 IU. And keep seing D3 is better. Can they be taken together? Is it safe?

simultaneous use of D2 and D3 
Doc just started me on the D2 50,000 IU once a wk, for a low Vit D level of 15. Can I also take simultaneous D3 2000 or even 4000 IU per day or would …

Falling D3 levels 
I have been taking 10,000IU of vit. d3 for 1 yr. in an effort to raise my level which was at 20. The first time i had my blood checked it had risen to …

How does the quality of vitamin D2 compare with D3? 
There has been a great deal of controversy regarding the quality of D2 compared with D3. Doctor Michael Holick, Professor of Medicine, Physiology and …

Switching from Vitamin D2 to Vitamin D3 
First of all, thank you for having the BEST website possible. I have spent many hours researching vitamin D information on hundreds of sites and yours …

Vitamin D3 and Chelated Calcium 
I can't drink milk products so I have to take calcium supplements. I also can't take just any calcium supplement because most of them upset my stomach. …

Vitamin D2 or D3? 
I have a vitamin D deficiency (total score .16; D2 was <.4 and D3 was .16). My Doc prescribed 50,000 Drisdol (D2) once a week but I had three days of upset …

D3 Instead of Prescribed D2 
I have been fighting a virus for several weeks. My doctor tested my vitamin D level and it was 8. She put me on 50,000 IU twice a week (prescription) …

Can taking Vitamin D3 correct Vitamin D2 deficiency? 
Thank you in advance for your time. My doctor tested me for Vitamin D and it and Vitamin D3 both came back at 20 ng/ML (on the borderline with existing …

Vitamin D3 Bioavailability 
My level of Vitamin D is 11.6. My physician wants to prescribe Drisdol (D2) 50,000 IU. After reading your information on Vitamin D2 vs D3, I asked …

Difference between Vitamin D an Vitamin D3 
Any difference to these two types of Vitamin D? My family doctor found out my Vitamin D level is very low; I started to take Vitamin D3 for 2000iu per …

Blood test proof that D2 worked better than D3 for me contrary to what you say 
I was tested(25 HydrxyOH) in May and found to be deficient Level 26.6 put on Vit D2 for 6 weeks(50,000 X 6) and then retested 2 mos later and my level …

My Doctor Said Not to Use More Vitamin D3 
Which is better D3 or D2? My doctor has prescribed 50,000 iu vitamin D2 for 12 weeks. It has been 8 weeks and my levels have not increased. No my doctor …

You are Using the Wrong Science. Vitamin D2 is equally as effective as Vitamin D3 
Read this study : Study Says D2 is as Effective as D3

One A Day Women's 50+ Advantage 
One A Day Women's 50+ Advantage. This vitamin pill has 800 I.U. of cholecalciferol. What a surprise! Photo by Jo-H

Vitamin D3 and Vitamin D2 dosages 
My Vitamin D blood level is 20 ng/ml. My doctor prescribed 50,000 iu three times a week for 16 weeks. According to what I'm reading, this is Vitamin D2. …

Vitamin D Prescription 
If OTC vitamin D3 is better to restore Vitamin D deficiency, why would my doctor prescribe Vitamin D 50,000 IU twice a week? My level is 7 ng/ml, I am …

Supplement with D2 or D3? 
My rheumatologist prescribed 50,000 IU capsules to be taken 1 per week for 5 weeks, in response to my Vitamin D levels of 11 ng/ml. She prescribed ergocalciferol. …

Vitamin D or specifically Vitamin D3? 
I was originally diagnosed with Multiple Sclerosis in 1994 and in 2009 was rediagnosed with Transverse Myelitis. My symptoms are Very similar to MS although …

Over the Counter Vitamin D 
I had my yearly blood work and this is the first year for checking my vitamin D level. They told me that my level was 31 ng/ml and told me to take a prescription …

vitamin D3 vs. Vitamin D 
Photo by Duncan I am a 49 year old man, and my Vitamin D Blood Level is 17.8 ng/ml. My doctor recommended that I take Vitamin D3 4000 …

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