Who’s Most at Risk
Worth extra attention if any of these apply:
- Adults over 60 — stomach acid declines with age
- Vegetarians and vegans who don’t supplement — B12 is almost exclusively in animal foods
- Anyone on metformin — long-term use lowers absorption
- Long-term PPI or antacid users
- People with pernicious anemia — the autoimmune cause
- Crohn’s, celiac, or other absorption disorders
- Anyone who’s had stomach or intestinal surgery, including weight-loss surgery
The more of these that apply, the lower the bar for getting tested.
Foods Rich in B12
For people who absorb it normally, food is the foundation:
Richest sources: beef, liver, salmon, tuna, sardines, and other animal proteins. Also good: eggs, milk, yogurt, and cheese. For plant-based eaters: fortified breakfast cereals and fortified plant milks — but read labels, and don’t rely on them alone if you have risk factors.
The crucial caveat: if your problem is absorption, more B12 in your food won’t fix it. Pernicious anemia and post-surgical deficiency need supplements or injections that bypass the broken step — no amount of steak resolves them.
When to See a Doctor — and What Treatment Looks Like
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See your provider for persistent tingling, unexplained fatigue, mouth changes, or memory and mood shifts that don’t lift — especially with any risk factor above.
A simple blood test checks your level. If you’re on metformin or a long-term acid reducer, it’s reasonable to ask for that test proactively rather than waiting for symptoms. If your provider is thorough, they may also check for the cause — testing for pernicious anemia — rather than just topping you up and moving on.
Treatment fits the cause: dietary change and oral supplements for mild dietary shortfalls, and B12 injections for absorption problems or severe deficiency, since they skip the gut entirely. Most people feel meaningfully better within weeks — the key qualifier being that nerve damage reverses only if it’s caught before it sets.
The Bottom Line
B12 deficiency touches the nervous system, the blood, and the brain, and it does it slowly enough to be mistaken for stress or age for years. Tingling hands and feet, unshakable fatigue, a smooth or sore tongue, and hair thinning are four signs worth knowing — most meaningful when several appear together.
Two things set this deficiency apart. It has a deadline — nerve damage can become permanent, so early matters more than with almost any other vitamin. And it’s frequently caused by common medications, metformin and acid reducers above all, not by diet. If those describe you, a cheap blood test is one of the more worthwhile things to ask for at your next visit.
This article is for general information and isn’t a substitute for advice from a qualified healthcare professional.
