Tinnitus can be a symptom of B12 deficiency (when B12 levels are low, the sheath around your nerves starts to deteriorate, and can cause things like tinnitus, visual problems (auras etc), pins and needles in hands and feet etc, also anxiety, memory loss… ultimately it can be dreadful.
I have found that having an infection or virus can really wipe my B12 levels out. I have a functional B12 deficiency (not often diagnosed, as GPs don’t run the tests required), and also have problems absorbing B12 (because of autoimmune issues). My symptoms tend to be tinnitus, visual issues, pins and needles in feet and lower legs, anxiety, hair loss, muscle weakness... It seems to have got worse during perimenopause (i think this is typical for women, that B12 issues come to the fore at this time).
The problem in the UK, GPs often don’t test the correct thing (they test serum B12 levels, which show both the available B12, but also the unavailable B12; rather than testing for active B12); and when they test, they seem to use much lower thresholds for when there is a deficiency…. ie with a certain set of results, you woukd be told by a GP in the UK that you are within normal range, but elsewhere in the world they would say that it was a deficient level.
Honestly, I could rant about this for ages, it is so frustrating.
If it was me, I would go to your GP with your list of symptoms, and ask for B12 deficiency, and functional B12 deficiency to be ruled out. DO NOT take ANY vitamin supplements while you are being investigated (as this can mask an underlying problem, in blood tests).
If you seriously get no joy from your GP (ie your test results come back ‘just within normal range’), but you still have symptoms, it is still worth asking again for them to treat it (if you have nerve damage symptoms (eg tinnitus, visual issues, pins and needles or numbness) then this needs to be with vit B12 injections, regular loading doses over the course of two weeks, then regular injections after that (they usually offer injections every 3 months in NHS)).
If all else fails, then aesthetic clinics offer B12 injections - as a beauty / health boost product, rather than a medicine to treat an illness. So you could always find a clinic near you and pay privately for injections as a ‘health boost’ to see if it stops your symptoms.
The B12 deficiency / pernicious anaemia forum on health unlocked website is also very useful..
Sorry for long post! Rant over now.. ;)
Edited to add: I am not a medical professional :)