Help - hoping Doc will do Intrinsic Factor test

[queenmabroo]

Hi all! Long time user of the Thyroid UK HealthUnlocked forum, first time poster over here.

I am diagnosed hypothyroid (I think it's hashimotos due to antibody flares) and over the years have had low vit D and low B12. I'm aware that with hypothyroid it's important to have good vitamin levels to help absorption. Not currently supplementing, a) because I'm terrible at keeping this routine and b) because I'm trying to sort through some tests.

Over the past few months I've been feeling lethargic, low mood, poorly powered in my body, breathless at exercise that used to be easy, dizzy, and weird body things. I did a medichecks thyroid ultravit in middle of July, and whilst my thyroid came back okay except for an antibody flair, my active B12 was almost out of the lower end of the range:

VITAMIN B12 - ACTIVE

16 Jul 2019

49.6

pmol/L 37.5 - 188 R

Given the amount of PA symptoms I had, and that we have a family history of PA, I went to the doctor to ask for investigation into this. He did a full raft of blood tests which happened today, but the B12 (total) came back as follows:

Serum vitamin B12 level 502 ng/L [211.0 - 911.0]

I have been feeling a lot better since Friday (less dizzy and with more energy), but still have a lot of symptoms of low B12. I'm absolutely happy to start supplementing myself (I've got a pack ready and waiting!) but I'm aware that taking them would disrupt any intrinsic factor testing.

The doc agreed that if this NHS test come back low then he'd order the IF test, but I don't think he's going to view that as low (just under halfway through range). I'm really keen to just rule out with PA is a cause, so I wondered if any of you could provide me with any evidence or anything that would help me argue my case with the doctor?

Thank you in advance!

[fbirder]

The Active B12 test is supposed to be much more precise and accurate than the serum test. Your result is about 130% of the bottom of the range, so not where you'd expect a deficiency.

Your serum B12 test is above average (normally around 350 ng/L) so I'm sure your doc will say that you do not have a deficiency.

You could ask for an MMA test (methylmalonic acid is used up in a reaction mediated by B12, so low B12 means high MMA)

[queenmabroo in reply to fbirder]

Hi, thanks for responding.

Can you tell me how you've worked out that percentage? I'm not sure.

Are docs more likely to do an MMA test than an IF test? I'm currently considering just paying for the IF test privately through medichecks as I don't think the doc is going to want to investigate further.

[fbirder in reply to queenmabroo]

The percentage is (49.6 / 37.5) x 100

The problem with the IFAB test is that a negative result will tell you nothing. For it to be positive you'd need to have a B12 deficiency caused by PA and be one of the 50% of that group who test positive (half of all people with PA test negative).

A high level for MMA is a good indicator of a B12 deficiency, although there are other possible causes. You can get the MMA test done privately.

Edit: Just looked at Viapath and they do a serum B12, Active B12 and MMA test for £90 - but they also say "Please note that MMA can be also elevated independently of vitamin B12 deficiency e. g. in thyroid disease, renal impairment, some genetic conditions, intestinal bacterial overgrowth or hemoconcentration."

So it may not be for you. I'd give them a ring.