B12 will stay in your bloodstream for around 4 months. So any 'high B12 doses' like 1,000mcg or sublingual will stay in your system for a long time.
One week off tablets is unlikely to make any difference - your levels would be roughly the same.
In reality, the small amount you've been taking in fortified foods or multivitamin tablets is unlikely to give you high levels.
Bear in mind that some people believe, including me, that healing from deficiency only happens when levels are in excess of 1,000, and are sustained at that level. And most people with unusually high levels tend to be in the thousands.
You're above range but not in a particularly drastic way. So if you have a healthy diet of red meat, chicken, pork, fish and eggs and milk you may well give yourself healthy b12 levels.
Also - each lab uses different ranges. So there is no ultimate 'maximum range'. It can vary.
Yes I have many conditions. I've had ME/ chronic fatigue for over 20 years. Hashimoto's but still struggle with energy on optimal amounts of t3 ( faulty Dio2 gene from both parents.Tingling in limbs for years.
I suspect there are some complexities that would warrant a medical team getting to the bottom of. Most of the community here have direct experience of deficiency more than excess.
But there is a risk of 'functional b12 deficiency' when levels are high and symptoms are felt. So tingling and numbness could be a symptom as its a classic b12d symptom, but we don't know since your bloods are roughly in the normal range, you have a normal diet and no absorption problems.
You may want to look into functional b12 deficiency and some other, more informed member, may help you with that. But perhaps getting a first response from your Dr would help since you have other conditions which may be playing a part
I have coeliac disease which I am very strict to treat . I also suffer with inflammation from esophagus down to duodenum from time to time. I've been prescribed Omeprozole which I only take if I'm desperate.Thankyou so much for your replies.
If your liver is damaged that can cause it to dump its stores of B12 - leading to elevated levels of B12. If you have kidney problems then this may result in an inability to remove excess B12 with the result that levels may either remain high or could even rise.The body has mechanisms in place that mean that overconsumption of dietary B12 is not going to lead to elevated levels of B12.
Use of very high dose supplements (>1000mcg per day) could potentially lead to raised serum B12, but this is unlikely to happen at 1000mcg a day - more likely with multiples of this dosage.
Some people will naturally sit above the normal range, because the normal range is a statistical average based on 90/95% of the population.
Please note that this forum is focused on Pernicious anaemia and other B12 absorption problems. It is a support forum rather than a place for professional medical advice. If you are concerned about the results then I would suggest discussing them with your GP. Running a liver and kidney panels isn't that difficult if you are feeling unwell.
Sorry for butting in I'm in UK. I have very low vit d , thyroid under active . Pernicious anemia. High platelets , Dr is doing lots if tests as had covid In Jan and feel I constantly have something stuck in my throat Dr is also saying my b12 is very high and wants .e to go on tablets . I told her I'm not stopping my injections
Cawest29 If you have had injections then that would be the cause of high B12. Tablets may not work if you have B12 - and even if they do work they are best started just after an injection.
I found a link from Elijahhawk 3 years ago which I think demonstrates better than anything I have read just how high b12 levels can be for many months after injections. It should put a few minds at rest.
I hadn't taken any high dose b12 for a couple of years. Just 50 mg doses for a few weeks. But stopped all supplimented 8 days before the test Morning mist.
Although that isn’t a high dose, for some people it might raise blood levels (but not alleviate symptoms of deficiency - as in the case of malabsorption). And 8 days isn’t long enough to clear much from your system. The link I posted was a study to show just how much people vary in their response to supplements (injections) and the length of time b12 can remain in the blood, over a year in some cases. Maybe you retain b12 longer than average. And as others have mentioned your result isn’t much over the range.
Functional B12 deficiency can be found by having B12 and methylmalonic acid (MMA) tested :
Possible B12 deficiency if B12 is low and MMA is high
Possible Functional B12 deficiency if B12 is high and MMA is high Possible renal problem if MMA is high : can be ruled out by blood test
Possible small intestine bacterial overgrowth (SIBO) if MMA is high: can be ruled out by about 4 hours of fasting breath tests, results of which should give you a yes/no on the day.
MMA, which is likely to be high when there is B12 deficiency, should quickly return to normal levels once the B12 has been replenished - so the loading injections should correct this. Functional B12 deficiency means that there is a problem with B12 and MMA linking in blood stream and being utilised at tissue/cell level. Which means despite B12, MMA will sit there uselessly in blood, and will continue to build up.
I don't know anything about renal problems other than a blood test can rule this out - this should be easy for a GP to organise. I'd get that one ruled out first.
SIBO bacteria will rob you of B12, and other vitamins. It can be treated with antibiotics, which can also deplete B12. They can also become immune to an antibiotic, so a series of courses varying the antibiotics used might be needed. You can see that ridding yourself of SIBO is not always easy.
All the above tests and treatment are NHS available.
If GP not able / willing to help, an appointment with a haematologist might be a good route. My original MMA test (I've had six) was ordered by my GP. It is unlikely to be able to be done at a local hospital - my GP tried three hospitals before successful. Because my MMA was raised despite frequent B12 injections and renal problems ruled out, and because my symptoms were worsening, I was given a functional B12 deficiency diagnosis and referred to a haematologist - who sent me for a SIBO test, and to a neurologist for MRI scan on brain and electric nerve testing.
I was also sent to consultants who look at DNA (Adult Inherited Metabolic Diseases).
They did my 6th MMA test - which was finally within range - but this was more than three years after my B12 injections had started. By then, I'd been self injecting every other day for almost two years. I expect that is what finally made the difference.
Because of this, my serum B12 remains above the measurable amount - over 2,000 ng/L.
Just to say you are not on your own, i have high b12 levels, which have increased since 2018. For the last 2 year blood tests results2000>. ( 200 -900 ) " No supplement taken."
Dr's do not have an answer to why, I was told to sit and wait, for what ??
Did have 5 or6 b12 injections in 2015 due to low b12 levels.
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B12 very high with normal blood results?. 
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