How do you test for b12 absorption?: How can I... - Thyroid UK

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How do you test for b12 absorption?

Gophe profile image
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How can I test my b12 absorption? I had my b12 tested a few months ago and it looked normal, but I have Hashimoto's and also tingling hands, dizziness, eye twitching, and gut issues -- all of which correlate to low b12. So I'm wondering if I'm maybe just not absorbing it. I've read that this can happen if you don't have enough intrinsic factor in your gut. But I'm not seeing a clear way to test for absorption. (Medichecks has one expensive test that includes intrinsic factor, but the website notes that it's for people who have a low b12 blood test result, which I don't.) Any advice?

EDIT: Just adding that my last serum vit B12 test was in May, and I had 724 ng/L, with the normal range being (200-900). My folate at the time was a bit high: 21.3 ug/L, with normal range being (2-17). I stopped taking my B12 supplement for about 4 days prior to that blood test.

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Thenightowl profile image
Thenightowl

Any b12 supplements taken within 4 months can skew b12 test results. Excess folate shouldn't cause any issues as it's water soluble so your body flushes out what it doesn't need.

The intrinsic factor test is not accurate in 40-60% of tests.

Have you ever had a low b12 test in the past?

Gophe profile image
Gophe in reply to Thenightowl

I'm not sure I've ever had my b12 tested before, actually. Just looked through past records and not finding anything.

Thenightowl profile image
Thenightowl in reply to Gophe

Hmmm that's a tricky one, I raised my b12 very high (over 2000) with sublinguals and it takes ages to drop. But I was getting more and more symptoms. As I'd had repeated low tests since I was a teenager, and have never been vegan I was confident enough to start injections.

I was not treated for my deficiency as per the NICE guidelines over the years.

I've an MS diagnosis, so did my mum (who had untreated b12 deficiency).

MS has exactly the same symptoms as b12 deficiency.

4 days after injections the most intense buzzing in my feet and fingers stopped and balance is now back to normal too. Saying that, I still have minor tingling at times, and hands go a bit dead at night,but I've got awful circulation.

The Facebook group 'b12 wake up' are an excellent source of files, support and general info, it may be worth seeing what they say.

Sorry I can't directly answer your questions, but a very long period completely off supplements, with no energy drinks may possibly be the way to go.

I hope you find some answers.

Gophe profile image
Gophe in reply to Thenightowl

Thanks, this is helpful.

Marz profile image
Marz in reply to Gophe

Once on B12 test results will be skewed. Testing MMA and Homocysteine can help - if high in range can suggest low B12 at a cellular level ...

SlowDragon profile image
SlowDragonAdministrator in reply to Gophe

Might be worth testing MMA and homocysteine here

nutris.viapath.co.uk/pages/...

Gophe profile image
Gophe in reply to SlowDragon

Okay, thanks Marz and SlowDragon . SlowDragon, to your question below: I moved up to 75mcg of levo a few months ago. Just had a new test last week. Dr. left a messg saying results are normal, but I haven't gotten the printout yet, so not sure what the exact levels are. Will try to get those tomorrow so I have a bit more clarity.

SlowDragon profile image
SlowDragonAdministrator

Looking at previous posts, are you still only on 50mcg levothyroxine?

This is only a STARTER dose

Bloods should be retested 6-8 weeks after each dose increase

The aim of levothyroxine is to increase the dose slowly upwards in 25mcg steps until on somewhere around full replacement dose (typically as minimum of 100mcg, unless extremely petite)

Levothyroxine doesn’t top up a failing thyroid, it replaces it. So it’s essential to be taking high enough dose

For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also EXTREMELY important to test vitamin D, folate, ferritin and B12

Low vitamin levels are extremely common, especially if you have autoimmune thyroid disease (Hashimoto's) diagnosed by raised Thyroid antibodies

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .

Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw).

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip)

Is this how you do your tests?

Private tests are available as NHS currently rarely tests Ft3 or thyroid antibodies or all relevant vitamins

List of private testing options

thyroiduk.org/getting-a-dia...

Medichecks Thyroid plus vitamins including folate (private blood draw required)

medichecks.com/products/thy...

Thriva Thyroid plus antibodies and vitamins By DIY fingerpick test

thriva.co/tests/thyroid-test

Thriva also offer just vitamin testing

Blue Horizon Thyroid Premium Gold includes antibodies, cortisol and vitamins by DIY fingerprick test

bluehorizonbloodtests.co.uk...

If you can get GP to test vitamins and antibodies then cheapest option for just TSH, FT4 and FT3

£29 (via NHS private service ) and 10% off if go on thyroid uk for code

thyroiduk.org/getting-a-dia...

monitormyhealth.org.uk/thyr...

our thyroid controls our metabolism

As an example....if, when perfectly healthy, your own thyroid made the equivalent of 125mcg levothyroxine....and this metabolism is controlled by pituitary sending messages - TSH (Thyroid stimulating hormone)

Then as your thyroid starts to fail (usually due to autoimmune thyroid disease) ....you might get diagnosed when your thyroid has reduced output to roughly equivalent of 75mcg levothyroxine

Pituitary has noticed there’s a drop in thyroid hormones in the blood....(that’s Ft4 and, most importantly, the active hormone Ft3) ....so to try to make more thyroid hormone ...pituitary sends out stronger message to thyroid - TSH rises up

When GP starts you on 50mcg ....initially you feel a bit better ....as you have 75mcg from your own thyroid and 50mcg levothyroxine

But (here’s the bit some GP’s don’t understand)....levothyroxine doesn’t “top up” your own thyroid output.....well it does very briefly....but the pituitary very soon “sees” the levothyroxine in the blood....and TSH starts to drop

So at the end of week 6 ....TSH has dropped a lot. Your thyroid takes a rest ....has a holiday

So at this point you are now only mainly using the 50mcg levothyroxine....which is actually a dose reduction down from managing on 75mcg from your own thyroid before you started on levothyroxine

So you start to feel worse .....and are ready for next 25mcg dose increase in levothyroxine

Modern thinking ....and New NICE guidelines suggests it might actually be better to start on higher dose .....but many medics just don’t read guidelines ....and many patients can’t tolerate starting on more than 50mcg and need to increase slowly. Starting on 50mcg and stepping dose up in 25mcg steps, retesting 6-8 weeks after each increase. But we still very often need to increase up to full replacement dose

nice.org.uk/guidance/ng145/...

1.3.6

Consider starting levothyroxine at a dosage of 1.6 micrograms per kilogram of body weight per day (rounded to the nearest 25 micrograms) for adults under 65 with primary hypothyroidism and no history of cardiovascular disease.

Aim is to bring TSH down under 2.5 as absolute maximum.

gp-update.co.uk/Latest-Upda...

Traditionally we have tended to start patients on a low dose of levothyroxine and titrate it up over a period of months.

RCT evidence suggests that for the majority of patients this is not necessary and may waste resources.

For patients aged >60y or with ischaemic heart disease, start levothyroxine at 25–50μg daily and titrate up every 3 to 6 weeks as tolerated.

For ALL other patients start at full replacement dose. For most this will equate to 1.6 μg/kg/day (approximately 100μg for a 60kg woman and 125μg for a 75kg man).

If you are starting treatment for subclinical hypothyroidism, this article advises starting at a dose close to the full treatment dose on the basis that it is difficult to assess symptom response unless a therapeutic dose has been trialled.

A small Dutch double-blind cross-over study (ArchIntMed 2010;170:1996) demonstrated that night time rather than morning dosing improved TSH suppression and free T4 measurements, but made no difference to subjective wellbeing. It is reasonable to take levothyroxine at night rather than in the morning, especially for individuals who do not eat late at night.

BMJ clear on dose required

bmj.com/content/368/bmj.m41

bestpractice.bmj.com/topics...

Gophe profile image
Gophe in reply to SlowDragon

SlowDragon since I have low ferritin (29 ug/L in a range of (15 -250)), I googled ferritin and tingling hands, etc, and it looks like the symptoms I've been having could just as easily be associated with low ferritin as low B12. My latest episode of eye twitching and hand tingling started after I went off meat for a couple of weeks and had blood drawn, so that would make sense if low ferritin was behind this. I've just had a bunch of chicken liver for breakfast and will see if that makes any difference.

In the meantime, I got my latest TSH result back yesterday. It's .98 miu/L in a range of (.35 - 4.78), so that gets me under the threshold of 1 that this group had previously advised. However, I haven't had my T3 or T4 measured in a while, so it seems like the right time now to get a Medichecks test and check those, too.

So really I just wanted to ask you 2 things: 1) Does it sound reasonable that ferritin is more likely to be the issue here rather than b12 absorption? And 2) Do you agree with my proposed course of action: work on increasing ferritin to see if symptoms improve, and get the full thyroid test from Medichecks to make sure I don't have super low T3/T4 that could be causing this?

(Unfortunately, my memory's not the greatest. I know I've posted about eating liver on this forum before and perhaps it helped my symptoms at the time and I noted that too but have since forgotten. I just looked through my past posts and interactions to check, but I'm not seeing anything related to ferritin. Is there a way to search my past posts/interactions by keyword?)

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