Can B12 shots not work? Worse, can B12 shots make you even more sleepy and tired than you were before you started the injections?
Answer is, absolutely not. Yet, it is a complaint you’ll hear quite often.
What gives?

Can B12 Injections Make You Tired?
No.
B12 shots work extremely well, but here’s an important thing to keep in mind:
Your concurrent B12-related symptoms and well-being are largely a snapshot of your B12 status 90 days ago. That’s because the life cycle of your red blood cells is 90 days. Every day, 90-day-old cells become obsolete, and are replaced by new, healthy cells. B12 plays a crucial part in their formation. So, if you only started injecting a month ago, then only about a third of your total red blood cells are ones that were generated under a healthy B12 status. Your anemia recovery will still be far from complete.
For that reason, you may still feel tired and fatigued, even a month or two into your B12 injections. And it’s even worse for people who don’t inject on a daily basis:
Vitamin B12 is water-soluble, so only a tiny bit is absorbed, and the rest is urinated out within hours. For that reason, you’ll want to inject daily. This way, you’ll keep B12 circulating in your system around the clock, ensuring adequate delivery to your cells and tissues, and the gradual correction of anemia. If you inject only once a week – or worse, once a month – you’ll barely see any improvement. This is crucial.
So, are your B12 injections not working? Chronic fatigue haunting you? Then injecting daily for 90 days straight, at minimum, is your first step.
You must go through that phase before you draw conclusions.
Also, Make Sure You Take The Right Forms
Methyl B12 and adenosyl B12 are the two most effective vitamin B12 forms. The two are native forms, and are superior to hydroxo B12 or cyano B12. Cyano B12 in particular should be avoided, especially in patients with pernicious anemia or generally with high homocysteine. The depletion of glutathione – necessary to remove the cyanide from cyano B12 – may increase homocysteine, thus only making things worse for them.
We like methyl B12 the most, because it comes bundled with a valuable methyl donor, a detoxifying agent to further boost your health. Also, in most people, methyl and adenosyl B12 can inter-convert easily, so the exclusive supplementation of methyl B12 is enough in most cases. Methyl B12 is especially good in reducing homocysteine, thus solving two problems at once for many patients. For this reason, it is our form of choice here.
So, Nothing to Worry About?
If B12 injections are not working (while taking the right forms and doses), and if chronic fatigue is haunting you, and if you’re just not sure whether you should continue with the shots, you may have just not given them enough time. B12 shots can’t make you sleepy or tired, but B12 deficiency can, and is most likely the reason you suffer from the chronic fatigue in the first place. So keep injecting, daily, for at least three months, and only then gauge the improvement in the correction of your anemia and overall well-being.
Good luck.