What’s a good b12 level?

[Hsss7]

Now I know this is a piece of string type of question as everyone will have their own personal optimal level. My results (ng/l) don’t come with a range and I’ve done a bit of reading and seen anything from 160 (nhs) to 900 as minimum recommended levels. I’ve not seen maximums mentioned much.

Can you have too much (toxic or harmful) or is it just disposed of out of the body immediately if there’s no further “storage space” available in the individual?

From the experiences of those in these forum can I ask what is a reasonable minimum to aim for as a starting point and an upper figure by which time the majority of people would feel good and well? (subject of course to adjustment by symptoms and wellbeing)

[Gambit62 Administrator]

Your body will have a maximum capacity to remove B12 - if you put B12 in faster than this levels will build up.

If you don't have an absorption problem and have put excess B12 in so levels have built up then I would expect levels to drop after you have started supplementing. There is only so much B12 that your body can bind to one of the two proteins that allow it to either be available to your cells or be stored in your liver - anything over this will eventually be removed by kidneys etc. Once you get back to the level that is right for you then you are back to regulating levels using stores in the liver.

The rate at which excess B12 is removed varies a lot from individual to individual and 3-6 months is the period without supplementation recommended before any testing.

If you have an absorption problem (unlikely if the tablets had that big an effect on your serum B12 levels) then levels would just continue to fall and fall.

There is a significant overlap between the symptoms of type 2 diabetes and the symptoms of B12 deficiency and similarly with iron deficiency - ferritin being a good measure for iron deficiency. Questions would be

a) did sorting out the blood sugar levels result in the symptoms disappearing - in which case that would suggest that being prediabetic was the problem

b) has treating the iron deficiency had any impact on your symptoms?

Basically - as said by others on previous reply your GP seems to be doing the right things- tackling the obvious issues to see if those resolve things.

And on sublingual versus tablets - there is a slight increase on absorption from sublinguals - but this is the difference between marginally below 1% getting into your blood and marginally over 1% getting into your blood.

ncbi.nlm.nih.gov/pmc/articl...

[Hsss7 in reply to Gambit62]

Thanks for the explanation of how it works. Good to have confirmed that if you supplement more than your body can handle it is excreted without harm. The huge question is how do you know what level is right for you before you cease supplements, and subsequently test if the liver via diet can sustain it or not? Back to my original question of what’s a good general level to aim for and trial.

Im not sure the fact that the sublingual tablets obviously worked on me proves no absorption problems from food (why else would my levels have gotten so low?)

Re sublingual v oral I can only find 2 studies (your link and one other designed to lower homocysteine levels) comparing these routes and neither focus on malabsorption as the cause of deficiency. In normally absorbing subjects I would expect the two routes to have comparable efficiency. Perhaps a comparison with oral tablets may reveal something about me should I need to supplement again but I’m not keen to risk it not working in that situation and low levels fall yet further.

To answer your questions. My symptoms were extreme tiredness, brain fog and a mild level of depression. All quite non specific and potentially from any number of conditions.

A) my sugar levels (never that high: hb1ac 55mmol, fasting 7.3mmol at diagnosis) were reduced simultaneously with the b12 supplements. Yes I felt better but which achieved this result? Perhaps both. (Hb1ac since 3 months into treatment 43, b12 818 from 159 previously)

B) iron deficiency was not addressed then. Symptoms of tiredness have returned despite the temporary massive and lately smaller improvement in b12 and bgl control. Treatment via ferrous sulphate has commenced 2 weeks ago after years at the same borderline or low levels. No change as yet. (One previous attempt a few years ago with ferrous fumerate 3months of treatment raised levels from 6 to 13 which is the only range I have ever been tested as in)

I agree I need to raise the ferretin levels and reassess symptoms then. And also see what happens to the b12 next. Stabilise or reduce? Does stabilising mean it’s the right level for me though or simply it’s the highest it’s able to maintain via my diet alone regardless of requirements or optimal levels?

[Gambit62 Administrator in reply to Hsss7]

I didn't say that taking too much B12 isn't potentially harmful. For some people raising serum B12 levels can result in a functional B12 deficiency - lots in blood but something affects the efficiency with which it is transferred into cells meaning that not enough gets through.

Your original levels may have been low because that was the right level for you. There are a few outliers who will be fine with levels even below the bottom of the normal range because the normal range is based on stats that capture 80-90% of the population.

Appropriate levels of B12 are what is right for you - there is no way of predicting the serum B12 level that is appropriate for an given individual. The range is huge because people vary substantially. The only way you can really go is via symptoms and I'm afraid the symptoms you quote are very far from being unique to B12 deficiency.

The only real way of knowing for sure from serum B12 that someone has an absorption problem is to see levels dropping significantly overtime in the absense of prior supplementation. Other than that it would be trying to identify a particular absorption problem.

The study mentioned above involved patients with pernicious anaemia - ie patients with an absorption problem. The changes in serum B12 were very modest and seemed to plateau after 4 weeks at levels much lower than you managed to achieve.

[Hsss7 in reply to Gambit62]

Thanks. You given me lots to think about.

That study however is not about patients with pa. They were 30 participants with low serum levels. Half of which were vegetarian so diet rather than pa the main suspect in the deficiency. Only 5/23 failed the schilling test and only 2 of those had antiparietal antibodies. Indeed my levels did rise far higher over 2 months than theirs did over a month but I also took 5000mcg methycobalamin not 500mcg cyanocobalamain, 10 times more, so not a direct comparison.

How I wish we all got base levels taken whilst young and healthy. Sadly we only tend to get our first readings whilst not in the best health and have no way of knowing our personal optimal levels.

I guess I raise the rest of them to within range and back to at least my previous highest levels (Iron, folate, Vit D and keep an eye on thyroid). and see what b12 does and how I feel.

[Gambit62 Administrator in reply to Hsss7]

apologies - i scanned and misread - the article references a 1960s study in which it Swedish researchers looked at 74 patients with PA and showed clinical and haematological recovery using high dose oral. Unfortunately the actual study doesn't appear to be on line so no idea what the timescales were.