The Cod Liver Oil supplements I have say they contain 25% of the
recommended daily value for people.  The Ferretone bottle says it contains
500 IU per 3/4 tsp, the recommended dosage for ferrets.  Unfortunately I
can't find anywhere (after 20 minutes searching the web, including the
FDA site!) what the daily value for humans is in IU.
 
I do have personal knowledge of a ferret that suffered from Vitamin A
toxicity when given 3/4 tsp Ferretone daily.  I think 8 in 1 has reduced
the amount of Vit A in Ferretone since then.  Can anyone confirm that?
 
Vitamin A is not toxic in and of itself, but it can build up in the body
if given in excessive amounts over a long period of time.  Symptoms of
overdose include lethargy and dry brittle coat (this is from memory, I
know there is info out there somewhere about this).
 
Linda Iroff
Oberlin OH
 
[Moderator's note: The daily value for adult humans is 5000 IUs, but that's
a little misleading: my understanding is that this value depends on the
source of the vitamin and varies greatly.  For example, vitamin A in the
form of retinol has greater bio-availablilty than, say, vitamin A from
beta-carotene.  The 5000 IU figure assumes the vitamin A is derived from a
"typical" diet.  If I'm way off here, I hope someone will correct me.  BIG]
[Posted in FML issue 3346]