The "Vitamin A Reset Protocol" has been used for many years within the Autism community by many doctors.
It sounds scary at first (everyone "knows" that too much Vitamin A is super, super toxic. Right?) but once you look into it, you find that:
It's actually not the case that it is extremely toxic (context matters, as usual).
Vitamin D3 is very protective of toxicity from A (and vice-versa).
The WHO recommends very high and repeated doses of Vitamin A for infants and postpartum mothers (regardless of what anyone thinks of the WHO it seems unlikely that it could be argued that they're an organisation that is prone to be crazily gung-ho on potentially dangerous doses of supplements).
I have come across many accounts of this protocol fixing visual stims in particular.
It also often triggers virus infection like symptoms (fever and sometimes rashes that look just like mild measles) which subside in a day or two.
The thinking is that the Vitamin A finally allows the immune system to actively fight a latent viral infection that it has not had the resources to deal with up until then.
If doing the protocol and wanting to also add D and K2, you'd need:
Vitamin A:
https://www.mandimart.co.uk/products/vitamin-a-mycellized-liquid-5-025ius-per-drop-30mls-by-kirkman
(There is at least one other brand of high dose A but I only have experience with this one.)
A liquid D3 our US doc recommended:
https://iherb.com/pr/Nature-s-Answer-Vitamin-D-3-Drops-4-000-IU-0-5-fl-oz-15-ml/20745
An excellent K2 I've used for ages but our US doc also recommended:
https://iherb.com/pr/Thorne-Research-Vitamin-K2-1-fl-oz-30-ml/21592
Beware of getting the right K2: Thorne also sells a combined D3/K2 which is half the price and a fraction of the K2!
This is the A/D/K protocol that our US doc recommends for children with long term illness, which is a slightly less drastic version of the "classic" protocol.
Mycellized Vitamin A (Kirkman)
25 drops daily for 7 days.
Then 2 drops daily.
Repeat the high doses for 7 days every 6 weeks.
Liquid Vitamin D (Nature’s Answer)
25 drops daily for 7 days.
Then 2 drops daily.
Repeat the high doses for 7 days every 6 weeks.
Vitamin K2 (Thorne)
3-4 drops per day with food.
If I was starting this, I think I'd do maybe a week of the lower dose before doing the high, pulsed dose. I see no reason to go into it too hard (it almost never is).
Also, I personally would not continue with the high dose forever. I don't know how many times our doc recommends repeating the high dose but this is aimed at children with long term illness.
This is something you'll find several versions of online and is practiced widely in the ASD community.
But I'd always do A with D as they are protective of toxicity in each other.
And I'd always do D with K2 as K2 directs the calcium deposition triggered by D to the right tissues.
Toxicity of A is very, very, verrrry overblown. Look into it of course but when I did I was shocked to find how benign it actually is. There is some evidence that high dose A during pregnancy can cause birth defects but that's A) not the case with a child! And B) quite possibly wrong anyway (but I've not dug into it enough to have an informed opinion).
200,000 iu on 2 consecutive days. Best at the weekend as they can get rather feverish.
Repeat after 6 weeks, twice, for a total of three times.
This sounds like a lot but it’s actually remarkably similar to the WHO guidelines, albeit these don’t say on two consecutive days:
http://archives.who.int/eml/expcom/expcom15/applications/paediatrics/formulations/retinol.pdf
From that document:
The current recommendation for supplementation is:
< 6 months 50 000 IU.
6-12 months 100 000 IU.
> 12 months 200 000 IU
...
In children over 6 months of age:
100 000 IU every 4-6 months
Children >12 months of age
200 000 IU every 4-6 months
Postpartum women
2 doses x 200 000 IU within 6 weeks of delivery, minimum 24 hours between doses