Vitamin B12 quietly supports red blood cell production, nerve function, and the way your body turns food into energy. When levels drop, the symptoms are vague enough that many people live with them for months before anyone checks a lab.
Signs of low B12
- Persistent fatigue that rest does not fix
- Brain fog, poor concentration, or low mood
- Tingling or numbness in hands and feet
- Pale skin, shortness of breath, or a sore tongue
These overlap with plenty of other conditions, which is why symptoms alone are not enough to justify treatment.
Who tends to run low
- People eating plant-based or largely vegetarian diets
- Adults over 50, as stomach acid production declines
- Patients on long-term metformin or acid-reducing medications
- Anyone after bariatric surgery or with absorption conditions
How deficiency is confirmed
A serum B12 level is the starting point. Borderline results sometimes need a methylmalonic acid or homocysteine level to clarify the picture. Your provider reads those numbers alongside your symptoms and medications rather than treating a lab value in isolation.
Injections versus pills
Oral B12 works well for many people. Injections make sense when absorption is the problem, since an intramuscular dose bypasses the digestive tract entirely. Patients with true absorption issues often notice the difference within a few weeks, while patients who were never deficient usually notice nothing at all.
What dosing looks like
There is no universal schedule. Some patients start weekly and taper to monthly; others need only seasonal support. We recheck labs when appropriate so the plan is based on your numbers. Read more about B12 injections at La Dahlia.
Want your levels checked?
Book a virtual consultation and we will review your history, order labs when appropriate, and build a plan from there.
This guide is educational and does not replace medical advice. Treatment requires provider evaluation. For emergencies, call 911.