Vitamin B12 Deficiency: Symptoms, Causes, and What You Need to Know

When your body doesn’t get enough vitamin B12, a crucial nutrient for nerve function and red blood cell production. Also known as cobalamin, it’s not made by the body—you have to get it from food or supplements. Without it, your nerves start to misfire, your blood can’t carry oxygen properly, and your brain begins to fog up. Many people assume they’re fine if they eat meat, but that’s not always true. The real problem isn’t always how much you eat—it’s whether your body can absorb it.

Pernicious anemia, an autoimmune condition that blocks B12 absorption, is one of the most common causes. Your stomach needs a protein called intrinsic factor to grab B12 from food, and if your immune system attacks that protein, you’re at risk—even if you’re eating plenty of salmon, eggs, or dairy. Older adults, people who’ve had stomach surgery, and those on long-term acid-reducing drugs like omeprazole are also at higher risk. Even vegans who take supplements can still be deficient if they don’t absorb them well. It’s not just about intake—it’s about delivery.

Low B12 doesn’t always show up as classic fatigue. You might feel tingling in your hands, have trouble walking straight, or notice your memory slipping. These aren’t just "getting older" symptoms—they’re warning signs your nerves are starving. And because the damage can be permanent if left too long, catching it early matters. Blood tests can spot low levels, but sometimes the numbers look okay while your body still isn’t using it right. That’s why doctors sometimes check for methylmalonic acid or homocysteine, markers that rise when B12 isn’t working.

You’ll find posts here that dig into how B12 interacts with other meds, why some supplements fail, and how to tell if your body is actually absorbing what you take. Some articles talk about drug interactions that block B12—like metformin for diabetes or long-term proton pump inhibitors. Others explain why injections work better than pills for some people. There’s no one-size-fits-all fix, but knowing what to ask your doctor can make all the difference.