B12 shots deliver the vitamin directly into muscle, bypassing your digestive system entirely
A B12 shot puts the vitamin into your bloodstream through intramuscular injection, usually in the arm or thigh. This matters because it skips the stomach and intestines — the places where absorption problems happen. If your body struggles to pull B12 from food or oral supplements, a shot can raise your levels faster and more reliably than swallowing a pill.
The shot itself is small, quick, and typically given in a doctor's office or clinic. Most people feel nothing beyond a brief pinch. The dose is usually 1,000 micrograms (mcg), though your doctor may adjust based on your blood levels and the reason you need it.
Key Takeaways
- B12 shots work best for people whose bodies cannot absorb the vitamin from food — including those with pernicious anemia, celiac disease, Crohn's disease, or who have had stomach surgery.
- Shots raise B12 levels faster than pills and bypass digestive absorption problems entirely, making them the standard treatment when deficiency is severe or symptoms are present.
- Most people need shots every one to three months once their levels are restored, though frequency depends on the cause of the deficiency and your individual metabolism.
- Side effects are rare and usually mild — occasional soreness at the injection site or temporary flushing — because B12 is water-soluble and your body excretes excess amounts.
Who benefits most from B12 shots
B12 shots are most useful for people whose digestive systems cannot absorb the vitamin properly. This includes anyone with pernicious anemia (an autoimmune condition that damages the stomach lining), celiac disease, Crohn's disease, or inflammatory bowel disease. People who have had gastric bypass surgery, stomach removal, or certain bowel resections also cannot absorb enough B12 from food and typically need shots long-term.
Vegans and vegetarians who do not eat animal products may also benefit from shots, though oral supplements often work if absorption is normal. Older adults sometimes have reduced stomach acid, which makes it harder to extract B12 from food — shots can help, though not everyone over 65 needs them.
If your blood test shows severe deficiency (usually below 200 pg/mL) or you have neurological symptoms like tingling, numbness, or confusion, your doctor will likely recommend shots over pills because they work faster and more predictably.
How often you need shots and what to expect
The frequency depends on why you need B12 in the first place. People with pernicious anemia or absorption problems typically start with weekly or monthly shots for two to three months to build up their levels, then move to maintenance shots every one to three months for life. Someone treating a temporary deficiency from diet alone might need only a few shots spread over several weeks.
Your doctor will check your B12 level with a blood test before starting and then periodically afterward to see whether your current schedule is working. Some people feel better within days; others take weeks to notice a difference. Fatigue and brain fog usually improve before numbness or tingling does, and nerve damage that has been present for months may take longer to reverse.
You do not need to do anything special before or after a shot. You can eat normally, exercise, and take other medications. The injection site may feel slightly sore for a day or two, similar to a flu shot.
Comparing shots to oral supplements and other forms
Oral B12 pills and sublingual tablets (dissolve under the tongue) work well if your digestive system absorbs normally. They are cheaper, you can take them at home, and there is no needle. The downside: they take longer to raise blood levels, and they do not help if you have an absorption problem.
Nasal sprays and gels exist but are less common and not always covered by insurance. They may work for some people but are not standard treatment for deficiency.
Shots are faster, more reliable for people with absorption issues, and the standard medical choice when deficiency is moderate to severe or when symptoms are present. The trade-off is that you need an appointment and a needle, and shots cost more upfront — though insurance usually covers them when medically necessary.
What happens if you stop getting shots
If you have pernicious anemia or a permanent absorption problem, stopping shots will cause your B12 to drop again over weeks to months. Your symptoms will return — fatigue, brain fog, and eventually numbness or tingling if deficiency becomes severe. This is why people with these conditions need shots indefinitely, not as a one-time treatment.
If you were deficient because of diet alone and you now eat enough B12-rich foods (meat, fish, eggs, dairy, fortified cereals), you may not need ongoing shots. Your doctor can test your levels to see whether you can switch to oral supplements or food sources.
Side effects and safety
B12 is water-soluble, meaning your body uses what it needs and excretes the rest through urine. You cannot overdose on B12 from shots. Side effects are uncommon and usually mild: soreness or bruising at the injection site, occasional flushing or warmth, or very rarely a mild allergic reaction to an ingredient in the injection.
People with certain conditions — including Leber's disease (a rare eye condition) or untreated potassium deficiency — should not receive B12 shots without medical supervision. Tell your doctor about any existing health conditions or medications before starting shots.
If you have had an allergic reaction to B12 or any ingredient in the injection before, let your doctor know. They may use a different formulation or test you first.
Cost and insurance coverage
B12 shots typically cost between $30 and $100 per injection at a clinic or doctor's office, though this varies by location and provider. Insurance usually covers shots when a doctor prescribes them for a documented deficiency or a condition that prevents absorption. Medicare covers them for pernicious anemia and certain other conditions.
If cost is a barrier, ask your doctor whether you can get shots at a community health center or urgent care clinic, which may charge less. Some people buy B12 vials and syringes online and self-inject at home after training, which reduces the per-shot cost but requires comfort with needles and proper technique.
Frequently Asked Questions
How long does it take to feel better after a B12 shot?
Most people notice improvement in fatigue and brain fog within a few days to a week. Numbness and tingling take longer — sometimes weeks or months — because nerve damage heals slowly. If you feel no change after two to three shots, talk to your doctor about whether the dose or frequency needs adjustment.
Can I give myself B12 shots at home?
Yes, if your doctor trains you and prescribes them. You will need to learn proper injection technique, sterilization, and storage. Many people find this convenient and cost-effective, but it requires comfort with needles and careful attention to hygiene. Your doctor can show you how or refer you to a nurse for training.
What if I am vegan — do I need B12 shots forever?
Not necessarily. If you eat fortified foods (cereals, plant-based milks, nutritional yeast) or take an oral B12 supplement regularly, your levels may stay normal without shots. A blood test will tell you. Shots are usually only needed if your levels drop despite supplementation or if you have absorption problems.
Do B12 shots give you energy or help with weight loss?
B12 shots restore energy if you are deficient — that is, if low B12 is causing your fatigue. If your B12 level is normal, shots will not boost energy or metabolism. They do not cause weight loss. Some clinics market B12 shots for energy or weight loss, but this is not supported by evidence in people with normal B12 levels.
Can I get B12 shots if I am pregnant?
Yes. B12 is essential during pregnancy, and deficiency can harm fetal development. If you need shots, your doctor will continue them throughout pregnancy. B12 does not cross the placenta easily, so your baby's levels depend on your own stores and diet.