My wife is very deficient of Vit D. The doctor has prescribed the Vit D Capsule.
And the source of vit d is Either
Cod liver oil in GELATIN capsule (don’t halal animal’s or not) Or
Cholecalciferol extracted from lanolin found in sheep’s wool.
So will it be permissible to CONSUME any of these for MEDICAL REASONS ?
As-salāmu ‘Alaykum Wa-rahmatullāhi Wa-barakātuh.
In the Name of Allāh, the Most Gracious, the Most Merciful.
Commercially the gelatin used in most of the capsules and medication is animal based. This is not to say that there are no commercial products which may use plant or other gelatin However But since animal rennet is so widespread, a Muslim is liable to find out what ingredients are in the medication. Let me try to simplify the issue.
- If the gelatin is from a non-animal source, then it will be permissible.
- If the gelatin is from bones of those animals which are consumable by Muslims, then such gelatin is also halaal. Zabiha is not a condition for the gelatin from bones of these animals.
- If the gelatin is from the hide/skin of those animals which are consumable by Muslims, the animal needs to be slaughtered for the gelatin to be considered halaal.
- If the gelatin is from bones or skin of animals which we cannot eat (lions, tigers), then that gelatin is not permissible.
- If the gelatin is from any part of pork/pig/swine, it will never be halaal.
The best way is to call the company and confirm what type of gelatin is in the product and then make the decision. If one is not able to get such clarification, one should abstain from consuming any such product.
Lanolin from sheep wool will fall under the category of derivatives from such an animal which is consumable by Muslims. Hence lanolin from sheep wool will be halaal even if it was not slaughtered in the Shar’i manner.
In principle, one can only resort to medication through something impermissible when there is no alternative available. Since Vitamin D deficiency is a widely occurring medical condition there are numerous procedures to handle it. In the two choices which you have mentioned, lanolin seems to be safer option. Moreover, you should also consult with your doctor or nutritionist to advise you on a non-animal substitute as indicated by the link which you have provided.  Your nutritionist may also be able to determine food groups and help you establish a diet plan to increase your specific vitamin D to tackle the deficiency.
And Allah Ta’ala Knows Best
Mufti Faisal al-Mahmudi 
Checked and concurred by
Mufti Luqman Hansrot
(قوله وشعر الميتة إلخ) مع ما عطف عليه خبره قوله الآتي طاهر لما مر من حديث الصحيحين، من قوله – عليه الصلاة والسلام – في شاة ميمونة «إنما حرم أكلها» وفي رواية «لحمها» فدل على أن ما عدا اللحم لا يحرم فدخلت الأجزاء المذكورة، وفيها أحاديث أخر صريحة في البحر وغيره، ولأن المعهود فيها قبل الموت الطهارة فكذا بعده؛ لأنه لا يحلها
الدر المختار وحاشية ابن عابدين (رد المحتار) (1/ 206)
 In foods where animal products are not desired, an alternative compound is ergocalciferol (also known as vitamin D2) derived from the fungal sterol ergosterol. (http://en.wikipedia.org/wiki/Cholecalciferol#Industrial_production)