“B12 shots boost energy.”
B12 shots have not been shown to boost energy in people whose B12 is not low.
If your B12 is not low, a B12 shot will not give you more energy. Lasting tiredness is worth tracking down to its real cause, and low B12 is one cause a simple blood test can check.
If you are tired and fit one of the higher-risk groups, ask for a B12 blood test before paying for shots.
Talk to a healthcare professional if: you have been tired for weeks without a clear reason, or you also have numbness, pins and needles, balance problems, memory trouble or a sore tongue; or you are at higher risk of low B12 because you eat a vegan diet without fortified foods or supplements, have had stomach or weight-loss surgery, or take metformin, a proton pump inhibitor or an H2 blocker for stomach acid.
Trials of B12, including weekly shots, in people without a clear deficiency found no benefit for thinking or mood, and no good trial shows more energy. Confidence is limited because only one trial measured tiredness directly, and it tested shots of a B-vitamin mix rather than B12 alone.
B12 shots have not been shown to boost energy in people whose B12 is not low. They treat a real deficiency, which can cause tiredness, but extra B12 does not add energy.
A 2021 review of 16 trials in 6,276 people without a clear B12 deficiency found no effect of B12 on any area of thinking and no overall effect on depression. Two of those trials gave B12 as shots, 1 mg once or twice a week, and the rest used pills. Only one trial measured unexplained tiredness; it gave a B-vitamin mix as shots twice a week, and its single better score came from a group that started out worse than the placebo group, so it did not show a real benefit. True deficiency is a different situation: UK national guidance lists unexplained tiredness as a common symptom of low B12, and shots are standard treatment for some causes, such as when the stomach cannot absorb B12. Vitamin injections are offered at most IV spas: 162 of 255 spa websites reviewed in 2024.
- Markun S, Gravestock I, Jäger L, Rosemann T, Pichierri G, Burgstaller JM. Effects of vitamin B12 supplementation on cognitive function, depressive symptoms, and fatigue: a systematic review, meta-analysis, and meta-regression. Nutrients. 2021;13(3):923. DOI: 10.3390/nu13030923. PMID: 33809274. PMCID: PMC8000524
- National Institute for Health and Care Excellence (NICE). Vitamin B12 deficiency in over 16s: diagnosis and management. NICE guideline NG239. Published 6 March 2024
- Sivakumar A, Forman HP, Wang I, Lurie P, Ross JS. State Policies and Facility Practices of IV Hydration Spas in the US. JAMA Internal Medicine. 2025;185(12):1455-1461. DOI: 10.1001/jamainternmed.2025.5028. PMID: 41051745. PMCID: PMC12501857
- Shane-McWhorter L. Intravenous Vitamin Therapy (Myers' Cocktail). Merck Manual Consumer Version. Last updated July 2025