What diagnostic tests for B12?

[Dreambirdie]

Could someone remind me which tests are best to test B12 levels.... is it homocysteine and MMA--as in methylmalonic acid?

Thanks in advance for your response.

 

[Bead Dog]

Both of those tests can be done, but I think MMA gives a better indication of deficiency at a cellular level. I've read that urine MMA test is more sensitive than blood serum MMA.

 

[Valentijn]

@Dreambirdie - There's also holotranscobalamin, which is supposed to measure the amount taken up by cells, or that can be taken up by cells. Or something