Am I correct in thinking that if I have a B12 serum level of 500 then the active B12 level would be 150 and the inactive 350 as 70% is inactive and 30% is active
Am I being stupid in thinking this there must be something more medical to it than that someone please explain or just say yes TOPH you are right
I thought active B12 was generally nearer 20% of total B12. and this looks consistent with the normally quoted ranges. That would mean that a serum B12 of 500 would, on average, mean an active B12 of 100.
My understanding is that the ratio of active to total B12 has high variability between individuals, and probably contributes to the lack of reliability of the total serum B12 test.
my understanding is that active B12 is more sensitive than serum B12. However, in general the ratio is 20%. A significant variation from this ratio may be indicative of problems elsewhere in the metabolism of B12, eg problems binding B12 to make holo-T/TC2, meaning that not enough B12 is getting through to your cells.
From people's replies on this forum I don't think an accurate percentage of active B12 can be attributed to the serum B12 value it varies greatly person to person
On a personal note I think my active B12 value will be far lower than the 20% because I was taking B12 capsules 6 or 7 a day and I was still feeling dodgy as hell I am going to write a letter two guy's and St Thomas's Hospital in London because they have a B12 active specialist who also is involved with methyl malonic acid so hopefully after I write that letter my miss diagnosis will be identified
Most doctors that I have spoken to including specialists do not comprehend have learnt or understand the implications of active B12 I live in Scotland and you may or may not know that Scotland has the highest percentage of sufferers of multiple sclerosis in the world this is unbelievable should never happen and it is all caused by using the wrong test to diagnose someone which is what has happened to me and many many others.
From people's replies on this forum therefore I don't think an accurate percentage of active B12 can be attributed to the serum B12 value
Watch this space I will be updating the response from NHS England regarding the inadequacies of NHS Scotland
From people's replies on this forum I don't think an accurate percentage of active B12 can be attributed to the serum B12 value it varies greatly person to person.
If it didn't, and everyone actually had the same percentage - or very nearly so, there would seem to be little point in developing the Active B12 test. It would be no better than the standard serum B12 test that we already knew was unreliable. 
Believe me when I say this most doctors GPS and specialists included working at the NHS have never heard of and do not care about active B12 I have been told on numerous occasions that B12 is a Placebo and I have this in writing so they will continue to use the serum B12 test when actually the holotranscobalamin active B12 test needs to be done if you live anywhere outside of London you will not get this test there are only a few hospitals in Britain that do it two of them is in London guys and St Thomas's Hospital and University College Hospital no please tell me does this not reflect in the country's distribution of MS cases I do believe this to be the case
Just replying Toph as I wanted to follow your post to see how you get on xX
Serum B12 levels compared to active B12 levels 
B12 active test for P.A?
Top of Range Active B12
Very high active b12, off supplementing
When should someone do the Active B12 test.
