Stop taking vit b12 before blood test...?

[Molly161018]

I've just noticed that on the Medichecks website under their Advanced Thyroid Function test it states: "Do not take vitamin B12 for two weeks prior to this test"

Is this new? And anyone know why?! I knew you weren't supposed to take biotin containing supplements for a while before but b12 is a new one to me!!!

[Marz]

If you have been taking B12 then the test result will be skewed and of little use. Stopping for two weeks is not enough - around 3 months is often mentioned !

What was your B12 result before supplementing ? B12 is water soluble so difficult to overdose ...