Step I Schilling Test

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Dr. Edd P.

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Why do we give un-labelled Vit B12 IM on the first step of the Schilling test?

THANKS :]
 
The unlabelled IM dose is intended to saturate the transcobalamin receptors in the liver.

That way, the radiolabeled B12 will not be able to interact with these receptors, and will show up in the urine when you measure it (assuming no malabsorption).
 
The unlabelled IM dose is intended to saturate the transcobalamin receptors in the liver.

That way, the radiolabeled B12 will not be able to interact with these receptors, and will show up in the urine when you measure it (assuming no malabsorption).
Got it. Thank you very much.
 
Zkenpachi is right. You don't want any radio-labelled B12 to be absorbed into your organs(esp. liver). Just make them stay in your blood, and then urine 🙂.