There are two ways to get enough vitamin B12: from food — meat, fish, eggs, dairy and fortified foods — and from supplements, as tablets, sublingual drops or injections. If you are over 50, vegan, have taken metformin or an acid reducer such as Pantoloc or Nexium for more than a year, or had weight-loss surgery, rely on a supplement or fortified foods rather than diet alone: the B12 in them is not bound to food protein, so it is absorbed even when stomach acid is low — which is exactly what fails in these groups. For most other adults, food covers the daily 2.4 µg easily: a 75 g serving of salmon alone provides about 4 µg. Its limit is absorption: 10% to 30% of older adults have atrophic gastritis and can no longer release B12 from food, and symptoms such as fatigue, a sore tongue and tingling feet develop so slowly that people blame age or stress. If you already have these symptoms, ask your doctor for a blood test before you start supplements — Canadian labs report B12 in pmol/L, and Health Canada uses 148 pmol/L as the cut-off for low levels.
Symptoms of Vitamin B12 Deficiency
B12 is needed to make red blood cells and to maintain the myelin sheath around nerves, so a shortage shows up in two ways. Low red blood cell production causes megaloblastic anemia — large, immature cells that carry oxygen poorly — which explains the tiredness and breathlessness. Damage to nerves explains tingling, numbness and balance problems, and it can happen even when your blood count is still normal.
- Hands and feet: pins and needles that start in the toes or fingers and spread upward. If this is your main symptom, our guide to pins and needles in feet covers other causes too.
- Walking: feeling unsteady in the dark or when you close your eyes, because the nerves that report foot position are affected first.
- Tongue: glossitis — a smooth, beefy-red, sore tongue — is a classic but often missed sign.
- Mind: memory lapses, low mood and, in older adults, confusion that can be mistaken for dementia.
Who Is at Risk and Why
| Risk factor | Why it lowers B12 | What to do |
|---|---|---|
| Age over 50 | 10–30% of older adults have atrophic gastritis and absorb little B12 from food | Get B12 from fortified foods or a supplement |
| Vegan or mostly plant-based diet | B12 is found naturally only in animal foods | Use fortified plant beverages or nutritional yeast and a supplement |
| Long-term metformin (e.g. Glucophage) | Reduces B12 absorption in the gut | Ask about B12 testing every few years; don’t stop the drug |
| Acid reducers taken for over a year (Pantoloc, Losec, Nexium, Tecta, Pepcid) | Less stomach acid means less B12 released from food | Ask your doctor or pharmacist whether you still need the drug and whether to test B12 |
| Pernicious anemia (autoimmune) | No intrinsic factor, the protein needed to absorb B12 | Lifelong treatment with injections or high-dose tablets, as prescribed |
| Gastric bypass, sleeve or bowel surgery; Crohn’s or celiac disease | The parts of the gut that absorb B12 are bypassed or inflamed | Regular monitoring and supplements set by your care team |
| Pregnancy and breastfeeding on a vegan diet | Needs rise to 2.6 µg and 2.8 µg a day; babies can be born with low stores | Prenatal supplement containing B12; tell your prenatal care provider about your diet |
How Vitamin B12 Deficiency Is Diagnosed in Canada
The first test is serum vitamin B12, usually ordered with a complete blood count: large red blood cells (a high MCV) support the diagnosis. Results between roughly 150 and 220 pmol/L are a grey zone, so many labs add methylmalonic acid (MMA), which rises when cells lack B12. Several provinces limit B12 testing to people with a clear reason — symptoms, risk medications, gut surgery, a strict vegan diet or older age — so tell your doctor exactly which applies to you. If B12 is low, your doctor may also test for intrinsic factor antibodies to rule out pernicious anemia, because it changes the treatment.
Vitamin B12 Supplements: Which Form to Choose
Supplement labels can look alarming: tablets sold in Canada often contain 250 to 1,000 µg, hundreds of times the daily need. That is normal. Your body absorbs only a small share — about 10 µg from a 500 µg tablet in a healthy person — and no upper limit has been set because excess B12 leaves in the urine. Your doctor or pharmacist will choose the strength and schedule; the table helps you compare the forms.
| Form | Best for | What to know |
|---|---|---|
| Cyanocobalamin tablets | Most people, including treatment of many deficiencies | The most studied and least expensive form; very stable |
| Methylcobalamin | People who prefer it | No proven advantage over cyanocobalamin for most people |
| Sublingual tablets, sprays, drops | People who dislike swallowing pills | Absorbed about as well as swallowed tablets, not better |
| B-complex or multivitamin | Prevention in people over 50, vegans, pregnancy | Contains smaller amounts — fine for prevention, often not enough to correct a deficiency |
| Injections | Severe deficiency, nerve symptoms, pernicious anemia, malabsorption | Given at a clinic or at home as prescribed; high-dose tablets can work as well for many people |
Choose a product with an eight-digit Natural Product Number (NPN) on the label: it means Health Canada has assessed it for safety, efficacy and quality.
Best Food Sources of Vitamin B12
| Food | Serving | Vitamin B12 | % of daily 2.4 µg |
|---|---|---|---|
| Clams, cooked | 75 g | about 74 µg | over 3,000% |
| Beef liver, cooked | 75 g | about 62 µg | over 2,500% |
| Rainbow trout, cooked | 75 g | about 4.8 µg | 200% |
| Sockeye salmon, cooked | 75 g | about 4.2 µg | 175% |
| Light tuna, canned in water | 75 g | about 2.2 µg | 92% |
| Beef sirloin, cooked | 75 g | about 1.2 µg | 50% |
| Swiss cheese | 50 g | about 1.6 µg | 67% |
| Milk | 250 mL | about 1.2 µg | 50% |
| Eggs | 2 large | about 1.2 µg | 50% |
| Fortified plant beverage, nutritional yeast, cereal | see label | varies | check % Daily Value on the Nutrition Facts table |
Values are converted to metric servings from U.S. National Institutes of Health data and rounded; actual amounts vary by product.
When to See a Doctor, Call 811 or Go to the ER
- Call 911 or go to the ER for sudden weakness or numbness on one side, confusion, trouble speaking, chest pain or severe shortness of breath — these need urgent assessment whatever the cause.
- See your doctor soon if you have tingling or numbness that doesn’t go away, balance problems, unexplained fatigue with pale skin, or a sore smooth tongue — especially if you are in a risk group above.
- Call 811 (Health Link, HealthLink BC, Info-Santé and similar services) to speak with a nurse if you aren’t sure how urgent your symptoms are.
This article is for general information and does not replace advice from your doctor or pharmacist. Do not start, stop or change prescription medicines because of B12 concerns without talking to your care team.
Frequently Asked Questions
What are the first signs of vitamin B12 deficiency?
Early signs are usually tiredness, weakness and shortness of breath on exertion, a sore or unusually smooth red tongue, and pins and needles in the hands or feet. Because these build up slowly over months, many people only notice them in hindsight.
Can I take vitamin B12 supplements without a blood test?
A standard daily B12 supplement or multivitamin is considered safe for most adults, and it’s the usual advice for vegans and people over 50. If you already have symptoms, get tested first: starting supplements before the blood test can mask a deficiency and its cause.
How long does it take to correct a B12 deficiency?
Energy often improves within a few weeks of treatment, and blood counts usually recover within about two months. Nerve symptoms such as numbness can take six months or longer, and some damage may be permanent if the deficiency lasted a long time — another reason to treat it early.
Is methylcobalamin better than cyanocobalamin?
There is no good evidence that methylcobalamin works better for most people. Cyanocobalamin is the form used in most studies, is very stable and costs less. Your body converts either form into the active forms it needs.
Can you take too much vitamin B12?
No upper limit has been set because no harmful effects have been linked to high intakes from food and supplements in healthy people; the excess leaves through the urine. Very high blood levels without supplements, however, can point to other conditions and should be discussed with a doctor.
Does metformin cause B12 deficiency?
Long-term metformin can lower B12 absorption, and a large trial found it reduced B12 levels by about 19%. If you have taken metformin for several years, ask your doctor whether to check your B12 — but don’t stop the medication on your own.
Do vegans need a B12 supplement?
Yes. Plant foods don’t naturally contain reliable amounts of B12, so vegans need fortified foods such as plant-based beverages and nutritional yeast, a supplement, or both — especially during pregnancy and breastfeeding.
Sources
- Health Canada — Dietary Reference Intakes tables
- Statistics Canada — Vitamin B12 status of Canadians
- Newfoundland and Labrador Lab Formulary — Vitamin B12 status
- NIH Office of Dietary Supplements — Vitamin B12 fact sheet