Vitamin B12 Deficiency
Low B12 can cause tiredness, anaemia, pins and needles, memory problems and a sore tongue. Common causes: a vegan diet, metformin, acid-reducing medicines and pernicious anaemia. Usually easy and cheap to fix.
The B12 ladder
Which step you need depends on the cause and how low you are. Nerve symptoms go straight to injections.
- Step 1 · Self-careB12 from foodMeat, fish, eggs and dairy, or fortified plant milks and cereals if you’re vegan.
- Works
- Not tested as a treatment; prevents deficiency but usually won’t fix one already there
- Cost
- Normal groceries
- How long
- For life, if you’re vegan
- Watch for
- Seaweed and spirulina don’t count: their “B12” is mostly the inactive kind
Spirulina smoothies are not a B12 plan.
- Step 2 · PharmacyHigh-dose B12 tablets (1,000 micrograms daily)For low B12 from diet or medicines.
- Works
- Raises levels about as well as injections in trials (Cochrane, low-certainty evidence)
- Cost
- About $10–25 for 2–3 months’ supply
- How long
- Recheck bloods after about 2–3 months; often long term
- Watch for
- Very safe. Not enough on its own for nerve symptoms or severe deficiency
Cheap, boring and effective. The holy trinity.
- Step 3 · PrescriptionB12 injections (hydroxocobalamin)For severe deficiency, nerve symptoms or pernicious anaemia: a loading course, then every 1–3 months.
- Works
- Corrects levels in nearly everyone; anaemia usually fixed within about 8 weeks. Nerves recover best when treated early
- Cost
- Under the $25 PBS co-payment, about $20 for 3 ampoules, plus the GP or nurse visit
- How long
- Loading over about 2 weeks, then ongoing, often for life
- Watch for
- A sore injection site. Rarely, allergy
A jab every couple of months beats nerves that don’t work properly.
- Step 4 · SpecialistFind and fix the causeTests for pernicious anaemia or coeliac disease, a review of metformin or acid-reducing medicines, and sometimes a gastroscopy.
- Works
- Not tested in trials; sensible step that stops it coming back and finds conditions that matter
- Cost
- Blood tests usually bulk-billed; specialist and gastroscopy costs vary (free in public, waits apply)
- How long
- Pernicious anaemia needs B12 for life
- Watch for
- Stopping medicines like metformin on your own. Don’t
Topping up without asking why is bailing water without finding the leak.
Save your money
Popular, heavily marketed or often asked about, but the evidence is weak or says no.
- Nasal sprays and patchesLittle evidence. Tablets or injections are preferred.
- B12 “energy” shots when your level is normalNo benefit. Your kidneys just send the extra down the loo.
- “Active” or methyl B12 at premium pricesNo good evidence it works better than ordinary B12 tablets. Same vitamin, fancier label.
- IV vitamin dripsNo evidence of benefit if your levels are normal, and you pay a lot for expensive urine.
What you can do
- Vegans and vegetarians: use fortified foods or a supplement.
- Don’t stop treatment just because symptoms improve.
- Don’t take high-dose folic acid on its own until your B12 is checked: it can hide the problem while nerves get worse.
See your GP if
- Tingling, numbness, unsteadiness or memory changes
- You’re pregnant or breastfeeding and vegan (low B12 can affect a baby’s development), or on metformin long-term
- Symptoms return
See a doctor urgently for new weakness, falls, or trouble walking.
Common questions
What are the symptoms of low B12?
Tiredness, anaemia, tingling, memory problems and a sore tongue are common. New weakness, falls or trouble walking need a doctor urgently.
Are B12 tablets as good as injections?
For low B12 from diet or medicines, a daily high-dose tablet (1,000 micrograms) usually works about as well as injections. Injections are needed for severe deficiency, nerve symptoms or pernicious anaemia.
Can metformin cause low B12?
Yes. Long-term metformin and acid-reducing medicines can lower B12. If you’ve been on metformin for a long time, it’s worth having your level checked.
How often are B12 injections needed?
After a loading course, usually every 1 to 3 months depending on the type. Pernicious anaemia and some other causes need B12 for life.
What causes low B12?
A vegan or mostly plant-based diet without supplements, pernicious anaemia (an autoimmune condition that stops B12 absorption), long-term metformin or acid-reducing medicines, coeliac disease, gut surgery and getting older.
What foods are high in B12?
Meat, fish, seafood, eggs and dairy. Plant foods don’t naturally contain useful amounts, so vegans need fortified foods (some plant milks, cereals and nutritional yeast) or a supplement.
Can you take too much B12?
B12 is very safe, and the body gets rid of what it doesn’t need. A high B12 level in someone not taking supplements is sometimes a clue to liver or blood conditions, so your doctor may look into it.
Helpful resources
- Pernicious Anaemia SocietyUK charity with plain-English information, a forum and support groups for people with pernicious anaemia. Free information; optional membership.
- Dietitians Australia: Vitamin B12Which foods have B12 and how vegans and vegetarians can get enough (fortified foods or a supplement). Free.
- NICE: B12 deficiency, the care you should expectPlain-English summary of UK guidance on testing, finding the cause and follow-up, handy for knowing what to ask. Free.
Evidence and more information
- Healthdirect: Vitamin B12
- Cochrane: Oral vs injected B12
- NICE: Vitamin B12 deficiency (2024)
- PBS: Hydroxocobalamin injection
maladywise.com/b12/