The short explanation
It is a good idea to ask for a test. B12 injections are a proper treatment when B12 is low, but weakness has many causes, such as anaemia from low iron, thyroid problems, diabetes, sleep problems, depression or simply overwork. If B12 is not actually low, injections are unlikely to help and may delay finding the real cause. A blood test for B12 and a complete blood count are simple and inexpensive. If B12 is low, a doctor can plan the right treatment and look for why it is low, such as a vegetarian diet, long-term acidity or diabetes medicine, or an absorption problem. If it is normal, the search for the cause of weakness can continue in the right direction.
What depends on your situation
The parts of this that change from woman to woman. Uncertainty is stated, not hidden.
- B12 injections are generally well tolerated, but repeated injections without a clear reason still mean cost, clinic visits and a missed opportunity to diagnose something else.
- B12 levels may already be high after several injections, so tell the doctor how many you have had before testing.
- Government hospitals and many labs offer these tests at low cost.
What this answer cannot determine
The boundary of online education. These need a clinician who can see you.
- This cannot tell you whether you need B12 or what is causing your weakness. Blood tests and a proper assessment are needed.
Questions for your clinician
Take these with you. You can add any of them to an appointment card.
- Was my B12 tested before starting injections?
- Can we check my blood count, iron and thyroid as well?
- If B12 is low, why is it low?
- How long would treatment need to continue?
When to seek help
Clinician-approved guidance for this topic. When in doubt, being seen is never the wrong choice.
Book an appointment soon
- See a doctor within a few days if weakness is worsening, or you have numbness, trouble walking or breathlessness.
Raise it at a routine appointment
- Book a routine appointment with a doctor who can test and explain the cause of your weakness.
Sources
The evidence this explanation is built on.
- Anemia MedlinePlus (US National Library of Medicine)
- Vegetarian diet MedlinePlus (US National Library of Medicine)
- Iron deficiency anaemia NHS
Who wrote and reviewed this
Every AskHer answer names its author. A clinically reviewed answer also names the clinician who signed it off — if no clinician is named below, it has not been clinically reviewed.
- Author
- AskHer Editorial (AI-assisted draft) AskHer's editorial team — not an individual clinician Works in English, தமிழ், हिन्दी
- Clinical reviewer
- Nobody yet No clinician has signed this answer off, and no person on the editorial team has read it yet. That is what the “Written with AI assistance” label means. It is queued for an editor to read, and then for a clinician who works in this area. The sources it was drafted against are listed above.
- Review status
- Written with AI assistance — not yet reviewed by a person
- Last reviewed
- Not yet reviewed by a person
- Version
- 1
Correction history
Substantive changes are listed, not quietly edited away.
No corrections have been made since this answer was first published.
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