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Will a B12 blood test one day after an injection appear falsely high?

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Old 09-01-2008, 09:10 AM   #1
Join Date: Sep 2008
Location: Pittsburgh, PA USA
Posts: 1
sept08 HB User
Question Will a B12 blood test one day after an injection appear falsely high?

Hello, I am new here and hoping someone may have some insight on this. I have always been low-normal B12 (tested in the 200 range). Since the lab reference range is 200-1100 doctor's have always said the B12 was normal and no treatment was necessary. Finally the doctor agreed since it was low/normal I may benefit from treatment and I began a series of B12 injections in Jan 08. At the time my latest level was 244. I only had 5 injections and then started traveling out of state frequently to help care for my ill mother and stopped going in for the injections but kept taking B12 supplements.

On 8-2-08 my B12 level was 282. On 8-22-08 I started the injections again and had the first one since February. The doctor also gave me a prescription to have the B12 test along with a check of homostein levels and methylmalonic acid. I also have hypothyroidism and went in on the morning of 8-23-08 for those test. I had the B12 lab work done at the same time. I got the results this week and it showed that on 8-23-08 my B12 level was 1547! I was shocked since it has always been in the 200 range and was 288 on 8-2-08. My question is could the blood test so soon after the injection give a false high reading? Could it have been an error? Is there a period of time you should wait after an injection before testing again to get a true reading?

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Old 09-01-2008, 06:09 PM   #2
Junior Member
Join Date: May 2008
Location: macon, ga
Posts: 19
abeliarose HB User
Re: Will a B12 blood test one day after an injection appear falsely high?

Hi Sept,

I'm sure you'll hear from others on this board who have lots of experience with B-12 issues. I can only give you my experience. I saw my doctor for anemia and she elected to give me a b-12 injection. The injection was given first, then within 15 minutes my blood was drawn for testing. The resulting B-12 value was off the scale at >2000. My doctor told me to wait one week before coming back for a recheck, it was still high at 931 (range 211-911). Two months later it was near the high end of normal at 816, which is probably typical for me. Obviously my B-12 level was not contributing to my anemia. So from my very limited experience, I would think your B-12 levels would still be quite high on the day following your injection. I wish you the best and good luck with your treatments.

Old 09-02-2008, 05:57 PM   #3
Senior Veteran
Join Date: May 2007
Location: FL
Posts: 2,379
Re: Will a B12 blood test one day after an injection appear falsely high?

I have heard that you have to wait for at least 2 weeks after injections before testing to get a true value. You didn't get a true reading. FLFLOWERGIRL

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