What is an optimal pmol\L level for ACTIVE B12.

[Diana49]

Thank-you.

[PlatypusProfit8077]

the range my lab gave here in Australia for active B12 was 59-150pmol/L but I’ve seen other references as 40-200 pmol/L

My active B12 was 56

[Gambit62 Administrator]

ranges can be specific to the machine running the test because of the way it has been calibrated. The normal range is where 90% of people are okay.

I don't think that optimal is a useful term to use in respect of B12 results if you are applying it to an individual. Optimal is what is right for you. B12 results have large ranges because people vary a lot in what is right for them, so picking a number out of the air and saying it applies to everyone as optimal just doesn't make sense to me.

[Cherylclaire Forum Support]

I looked at two papers re holo-TC (active B12) :

1) "Biomarkers and Algorithms for the Diagnosis of Vitamin B12 Deficiency" from Luciana Hannibal et al (2016) :

"Holo-TC represents 6-20% of the total vitamin B12 present in serum" (quoted from Nexo et al)

"The normal range of holo-TC in healthy subjects is 20 - 125 pmol/L " (quoted from Valente et al)

The diagnostic value of holo-TC as a first line test is questioned at this time by the authors, additional research required.

2) "The Many Faces of Cobalamin (Vitamin B12) Deficiency" from Bruce Wolffenbuttel et al. (2019) :

Discussing problems: ".... However, holoTC also has a large window with indeterminate levels and the reference values strongly depend on the assay method used. It has been suggested that patients with holoTC levels between 23 and 75 pmol/L require further testing of MMA levels to document, or rule out, true vitamin B12 deficiency. "

The superiority of holoTC over total serum B12 plus MMA is in question here.

Holotranscobalamin (holoTC) reference values as used for laboratory examinations (supplemental table 2) are given here as " intermediate: 32-70, normal 70- 125 pmol/L"

No doubt more research papers would give more of a variety and muddy the waters further - you can see why Gambit would not wish to select a definitive optimal figure.

My own active B12 >128pmol/L was described as adequate B12 replenishment.