Indeed. The D3 form is one you want. I actually had a endocrinologist prescribe the D2 form. Luckily my nutritionist has been following the literature for years.
And that incredibly low standard is also how the FDA set the "recommended daily allowance." Similar things are true for most other vitamins and minerals, as I recall.
Also, D2 causes overdose effects pretty easily, but you can take big multiples of the "RDA" in D3 (I think 10,000 IU/day for months for vitamin D deficiency has been mentioned) for quite a while without overdosing.
> you can take big multiples of the "RDA" in D3 (I think 10,000 IU/day for months for vitamin D deficiency has been mentioned) for quite a while without overdosing.
That's actually a problem, as people can become accustomed to taking large doses and then not understand why problems are occurring when they start way down the road.