It's interesting the different info given out by doctors.
I was told by my Specialist at St Marks that OTC Vit d is perfectly acceptable- it's the type you need individually that matters.
As a Health Visitor I was told to recommend OTC Vit d supplements to anyone I thought at risk after assessment. I can't scan and add my dept of health memo I was sent but this is very similar to what we were told:
PRESCRIPTION VITAMIN D
The prescription version of vitamin D is called Drisdol, and it comes in 50,000 IU capsules. It is commonly prescribed to be taken once per week. Drisdol is ergocalciferol, which is the form of vitamin D that is derived from plants. Ergocalciferol is often referred to as vitamin D-2. This is different than cholecalciferol, or vitamin D-3, which is the form that is synthesized in the skin with exposure to ultraviolet B rays.
OTC VITAMIN D
Both vitamins D-2 and D-3 are available in over-the-counter versions. They can easily be purchased in most drug stores/chemists and usually come in 400 IU, 1,000 IU, 2,000 IU or 5,000 IU capsules. Because the doses are smaller than the prescription version, the OTC versions are intended to be taken daily. OTC vitamin-D is relatively inexpensive.
D-2 VS. D-3
One difference between prescription and OTC vitamin D is that the prescription version is only available as D-2, or ergocalciferol. Many scientists believe that ergocalciferol and cholecalciferol are comparable in potency, but ergocalciferol is broken down more quickly in the body. Therefore, cholecalciferol, or D-3, may be slightly more effective to raise the blood levels of vitamin D.