How long before test?

[haggisplant]

Hello,

The private (medichecks?) thyroid all in test including b12 suggests to stop b12 for two weeks before testing.

Other online places seem to suggest 4 months!

Will 2-3 weeks be ok?

Will the fact that I’ve taken b12 supplements in the past before a test have skewed results?

I’m really suffering again with tingling and burning hands and feet, swinging between cold and hot, they then get stuck at hot and burn for hours or days. Need to investigate this properly. I’ve contacted the Gp but probably going round in circles.

I have hypothyroidism.

[haggisplant]

My last test was 521 ng/l, folate 12.

[fbirder]

What are you trying to find out by testing?

Are you trying to find out if you currently have low B12, despite the supplements. That will tell you that the oral B12 isn't being absorbed. In which case you don't need any delay. This will also provide important information. If your blood levels are sky-high with the supplements then you know that you can absorb the B12 from them.

Are you trying to find out if you would have a deficiency if you didn't take the supplements? Then you'll need to wait several months.

[haggisplant in reply to fbirder]

That’s a goo question, thanks.

I’m trying to find out if my peripheral neuropathy issues are linked to b12.

My last result in autumn 2019 was while taking 6ug a day in a multivitamin while breastfeeding. I wouldn’t have stopped it before the test.

Before children I actually took berocca which has 10ug.

Lately (3-4 mo ago) I changed to a different complex and dropped the b12 further. I didn’t think it was as an issue. Gradually my symptoms Ha be got worse. No idea if that’s a link.

If I stop for several months there’s a good chance it will be lower. Presumably I am absorbing from supplements. For breastfeeding you only apparently need 0.4 ug more, with an rda of 2.4 (from Kellymom website.)

But I’m not sure I can cope with worsening side effects.

Why would the medichecks test only ask you to stop for 2 weeks?

[haggisplant in reply to haggisplant]

Is 521 “sky high” on that amount of supplements?

[haggisplant in reply to haggisplant]

And I eat meat and eggs etc.

[Nackapan in reply to haggisplant]

It doesnt sound like b12 deficiency. On such a low supplement.

It seems you can absorb it.

It was good you took it whilst breastfeeding in a multivit as your b12 can go low after childbirth

.

Its a good level of b12 on such a low supplement. Another sign you are absorbing it.

Have you posted on the thyroid forum?

[haggisplant in reply to Nackapan]

No, but I’m not feeling this is a thyroid issue. I’ve been told by Gp to look at burning foot syndrome. Which can be caused by low b vits and hypothyroidism.

That test was full b12 not active b12. Does that make a difference?

[Gambit62 Administrator in reply to haggisplant]

521 would be off the measurable range for active B12 so obviously serum B12 - active B12 generally 1/5 of total serum B12 so which test isn't generally that important.

521 is actually quite high in the normal range which makes it rather unlikely B12 is the problem.

B12 levels in the blood are maintained at pretty constant levels in an individual using stores of B12 in the liver. An absorption problem also means that your ability to use those stores is compromised as release depends on the same mechanism as absorption from food. This means that serum B12 can be a useful test for identifying an absorption problem eg because it shows a significant drop in B12 over time. Significant her means more than 20% as this is the accuracy of the test for serum B12 - active B12 is a bit more accurate -

The doses of of B12 you have been supplemented are two low to have any appreciable impact if you do have an absorption problem so in this instance there isn't really much point in stopping. If you were taking doses of 1000mcg+ then 3-6 months without supplementation would be the general rule of thumb to follow to get a baseline

[haggisplant in reply to Gambit62]

Thank you for your reply. So an active b12 test might be helpful/ show a different picture?

I hadn’t been thinking b12 was an issue at all till I revisited the burning foot syndrome causes and noticed that there’s many links between the symptoms I’m experiencing and hypothyroidism and b12.

[Gambit62 Administrator in reply to haggisplant]

unlikely active B12 would really show more than serum B12, particularly in relation to B12 absorption

Note: amended

[haggisplant in reply to Gambit62]

I don’t fully understand that.

To be honest it doesn’t look like there’s much issue in taking the odd extra b12 and seeing if it helps. I’ve just looked at my b complex (together brand) and worked out that if I take two it’s closer to the Thorne one.

I’m getting the medichecks test for other reasons and will just follow what they say re stopping for 2 weeks prior to test.

[haggisplant in reply to haggisplant]

Do you mean serum b12 is just serum b12 and doesn’t give a better picture of what might be going on?

[JanD236 in reply to haggisplant]

I suspect gambit62 meant to say ‘unlikely active B12 would really show more than serum B12....’. Hopefully they will clarify.

[haggisplant in reply to JanD236]

Ok tbanks

[Gambit62 Administrator in reply to JanD236]

thanks JanD236 - must have had a typo moment