B12 and folate
B12 Deficiency Symptoms: The Full List
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed September 20265 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
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The NHS lists tiredness, breathlessness, headaches, palpitations, a sore or red tongue and memory slips. Low B12 adds nerve signs: pins and needles, numbness, muscle weakness and poor balance. They build slowly over months, so the change is easy to miss.
Not sure which markers you need? Build your test →You are tired in a way sleep does not fix. Your hands go to sleep at odd moments. Words you know go missing mid-sentence.
Each one on its own sounds like a busy life. Together they are on the NHS list for low vitamin B12, which is worth knowing about. If you are already taking a B complex supplement, that changes what a test can tell you.
1. What are the symptoms of low B12?
The NHS splits them into two groups. First the ones B12 shares with low folate, because both can make the same kind of anaemia. That overlap is also why a high folate can hide a B12 shortage while the anaemia looks corrected.
- Feeling weak or tired. The one almost everybody notices first.
- Rapid breathing or breathlessness. Stairs that never used to register.
- Palpitations and headaches. A heartbeat you can suddenly feel.
- A sore or red tongue, sometimes with mouth ulcers. Easy to blame on something you ate.
- Loss of appetite, indigestion, diarrhoea. Gut signs that rarely get connected to a vitamin.
- Problems with memory, understanding and judgment. The one people find most unsettling.
- Problems with your vision. Less common, and a reason to see someone promptly.
None of this is a diagnosis. Plenty of other things cause the same list, which our guide to being tired all the time walks through.
2. Why does it creep up on you?
Two reasons, and they compound.
The first is your store cupboard. The NHS says stores of vitamin B12 in the body can last around 2 to 5 years. So a change in what you eat, or in how well you absorb it, may take years to show up as anything at all.
The second is the pace. The NHS puts it plainly. Symptoms “usually develop gradually, but can worsen if the condition goes untreated”.
Gradual change is the hardest kind to notice in yourself. You adjust. By the time it is obvious, you have usually been living with it for a while.
3. Which symptoms point at B12 rather than folate?
The nerve ones. B12 helps maintain the coating around your nerves, so a shortage shows up in how they carry signals. The NHS lists numbness, pins and needles, muscle weakness, poor balance and coordination, incontinence, and psychological changes ranging from mild low mood or anxiety to confusion.
This is the part worth acting on rather than watching.
“Although many of the symptoms improve with treatment, some problems caused by the condition can be irreversible.”
The NHS notes that nervous system problems in particular can sometimes be permanent. That is the argument for asking the question early rather than giving it another six months. Our guide on tingling and numbness covers the wider set of causes.
4. Why does my tongue feel sore?
Because the cells lining your mouth turn over fast, and fast-growing tissue feels a B12 shortage early.
A tongue that looks smooth, red or beefy, sometimes with mouth ulcers, is on the NHS list. People often put it down to a hot drink or a new toothpaste for months.
It is a useful clue precisely because it is visible. If the sore tongue and the tiredness turned up in the same season, say so when you ask for a test.
5. Who is most likely to run low?
The NHS names four routes.
- Pernicious anaemia. An autoimmune condition that blocks absorption. The NHS calls it the most common cause of B12 deficiency in the UK.
- Diet. Meat, fish and dairy usually cover it. A vegan diet without fortified foods or a supplement does not.
- Gut conditions and surgery. Crohn’s disease and stomach surgery both get in the way of absorption.
- Some medicines. The NHS names proton pump inhibitors, metformin and nitrous oxide.
If you take omeprazole or another acid-reducing medicine long term, our guide on omeprazole and blood tests is worth a read. Eating vegan? See our vegan blood test guide.
6. Which markers actually answer the question?
B12 and folate together, because they cause overlapping symptoms and you cannot tell them apart from how you feel.
Helvy’s Vitamins & Minerals panel (£159) reports vitamin B12 and folate alongside the full iron set, vitamin D and magnesium. Our General Energy & Wellness panel (£149) reports B12 with thyroid, cholesterol, kidney and liver markers for a wider first look.
One honest limit. Neither is an anaemia screen. That also needs a full blood count and a clinical judgement. See a GP rather than testing at home if you have numbness, weakness or balance problems now.
Not sure which fits? The build-my-test tool walks you through it, and the energy and fatigue hub collects the rest.
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Stop guessing at the tiredness
Helvy’s home blood tests report B12 and folate next to iron and vitamin D, so you see which one is actually low. Samples are processed by UKAS-accredited UK labs.
Frequently asked questions
What are the first signs of low vitamin B12?
Usually tiredness and breathlessness, often with headaches or palpitations. A sore or red tongue and memory slips are on the NHS list too. The NHS says symptoms usually develop gradually.
Can low B12 cause pins and needles?
Yes. Pins and needles, numbness, muscle weakness and problems with balance are on the NHS list of nerve symptoms linked to low B12. See a GP about these rather than waiting.
Can low B12 affect your mood or memory?
The NHS lists problems with memory, understanding and judgment, and psychological changes ranging from mild depression or anxiety through to confusion. Many other things do the same, so the marker is worth measuring rather than assuming.
How long does it take to become deficient?
Slowly. The NHS says body stores of B12 can last around 2 to 5 years, so a dietary or absorption change may take years to show up in how you feel.
What is the most common cause in the UK?
The NHS says pernicious anaemia, an autoimmune condition that stops B12 being absorbed from food. Diet, gut conditions and certain medicines account for much of the rest.
Is the damage permanent?
Many symptoms improve with treatment, but the NHS says some problems can be irreversible, and names nervous system problems as the ones that can sometimes be permanent. That is why timing matters.
Related guides
Vitamin B12 Blood Test UK
What the test measures and how to read it.
Vitamin B12 Levels by Age UK
Where your number sits against the usual range.
B12 Injections UK
When injections are used instead of tablets.
Folate Blood Test UK
The vitamin that causes the same symptoms.
Tingling and Numbness Blood Test UK
The wider set of causes behind nerve symptoms.
MCV Blood Test UK
Red cell size, and why B12 makes it rise.
Related panels
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