Recovery from vitamin B12 deficiency varies from person to person. NICE advises that symptoms may start to improve within two weeks, although it can take up to three months to notice improvement. Some symptoms may take considerably longer to disappear completely.
The recovery time depends on:
- The cause of the deficiency
- How severe it is
- How long it was present before treatment
- Whether nerve-related symptoms are involved
- Whether vitamin B12 can be absorbed properly
- The treatment being used
- Whether another condition is contributing to the symptoms
Vitamin B12 deficiency should be diagnosed and treated with professional guidance. An ordinary food supplement may not be suitable when the deficiency is caused by poor absorption, autoimmune gastritis, surgery or another medical issue.
What does recovery from vitamin B12 deficiency mean?
Recovery can involve several different changes.
These may include:
- Vitamin B12 levels increasing
- Red blood cell production returning towards normal
- Tiredness and weakness improving
- Pins and needles becoming less noticeable
- Balance, memory or concentration improving
- The original cause of the deficiency being addressed
- Preventing symptoms from returning
These changes do not necessarily happen at the same speed.
Someone may notice that their energy begins to improve while numbness or balance problems take longer. Another person may have improved blood-test results before they feel completely recovered.
What is vitamin B12 deficiency?
Vitamin B12 deficiency occurs when the body does not have enough vitamin B12 to support its normal functions.
Vitamin B12 is needed for normal red blood cell production and nervous-system function. A deficiency can be associated with tiredness, weakness, pins and needles, balance problems, memory or concentration changes and a sore or red tongue. Vitamin B12 deficiency can sometimes be present without anaemia or enlarged red blood cells, so the absence of these findings does not automatically rule it out.
Symptoms can overlap with many other health conditions. Diagnosis may therefore involve a discussion of symptoms, risk factors and blood-test results.
How quickly can vitamin B12 treatment start working?
Vitamin B12 replacement begins increasing the amount of B12 available to the body soon after treatment starts.
For example, NHS guidance states that hydroxocobalamin injections start working straight away. However, it may take several days or weeks before vitamin B12 levels and symptoms such as extreme tiredness or lack of energy begin to improve.
This distinction is important:
- The treatment can begin working immediately.
- Noticeable symptom improvement may take longer.
- Complete recovery may take weeks or months.
- Some symptoms may not fully resolve when the deficiency was severe or present for a long time.
Typical vitamin B12 recovery timeline
There is no guaranteed timetable, but the following provides a general guide.
| Time after starting treatment | What may happen |
|---|---|
| First few days | Treatment begins increasing vitamin B12 availability, but you may not feel different |
| Around two weeks | Some people may start noticing symptom improvement |
| Several weeks | Tiredness, weakness or lack of energy may begin improving |
| Up to three months | It may take this long before some people notice a clear improvement |
| Longer than three months | Neurological or long-standing symptoms may continue improving gradually |
| Long term | Treatment may need to continue when the underlying cause has not been removed |
NICE advises that symptoms may start improving within two weeks but can take up to three months. It also warns that complete disappearance of symptoms can take much longer, and symptoms may occasionally feel worse initially before improving.
How long does vitamin B12 deficiency tiredness take to improve?
Tiredness related to vitamin B12 deficiency may begin improving within several days or weeks after appropriate treatment.
However, vitamin B12 treatment is most likely to improve tiredness when the deficiency is actually contributing to the symptom.
Tiredness can also be caused by:
- Poor or disrupted sleep
- Stress
- Iron deficiency
- Folate deficiency
- Thyroid conditions
- Diabetes
- Infection or illness
- Medication
- Depression or anxiety
- Other underlying conditions
Someone may therefore have corrected vitamin B12 levels but continue feeling tired because another factor is involved.
Persistent tiredness should be reviewed rather than managed by increasing vitamin B12 doses without professional advice.
How long do pins and needles take to improve?
Pins and needles, numbness, weakness and balance problems can be signs that vitamin B12 deficiency is affecting the nervous system.
These symptoms may take longer to improve than general tiredness. Recovery can continue for several months, particularly when the deficiency was severe or had been present for a long time.
Early diagnosis matters because some neurological complications caused by vitamin B12 deficiency may become permanent when treatment is delayed.
Seek medical advice promptly if you experience:
- New or worsening numbness
- Persistent pins and needles
- Muscle weakness
- Difficulty walking
- Poor balance
- Vision changes
- Memory or concentration problems
- Loss of bladder or bowel control
Do not wait for an over-the-counter supplement to work when neurological symptoms are present.
Can vitamin B12 symptoms get worse before improving?
NICE advises healthcare professionals to explain that symptoms can sometimes become worse initially during treatment, but that this should improve.
This does not mean that every worsening symptom is expected or should be ignored.
Contact your GP or treatment provider when:
- Symptoms are becoming significantly worse
- New symptoms appear
- Symptoms continue to interfere with everyday life
- You are unsure whether the treatment is working
- You experience a possible reaction to the medicine
NICE recommends reviewing alternative diagnoses or adjusting treatment when symptoms do not improve sufficiently, become worse or new symptoms develop.
Does the cause of vitamin B12 deficiency affect recovery?
Yes. Finding the cause is important because it influences the treatment, recovery process and whether replacement is needed temporarily or permanently.
Dietary vitamin B12 deficiency
A dietary deficiency can develop when someone does not regularly consume enough reliable vitamin B12 sources.
Vitamin B12 is found mainly in:
- Meat
- Fish
- Eggs
- Milk and dairy products
- Fortified breakfast cereals
- Fortified plant-based drinks
- Fortified nutritional yeast
- Other foods with added vitamin B12
People following vegan diets need a reliable source through fortified foods or an appropriate supplement.
When diet is the cause, treatment may involve oral vitamin B12 replacement alongside improving dietary intake. However, NICE advises healthcare professionals not to assume that a vegetarian or vegan diet is necessarily the only cause, as another absorption or medical issue may also be present.
When the dietary cause has been addressed and symptoms have improved, treatment may eventually be reviewed and possibly stopped under professional guidance.
Poor absorption
Some people consume enough vitamin B12 but cannot absorb it properly.
Possible reasons include:
- Autoimmune gastritis
- Coeliac disease
- Previous stomach surgery
- Bariatric surgery
- Removal of part of the intestine
- Other conditions affecting the digestive system
NICE recommends lifelong intramuscular vitamin B12 replacement when autoimmune gastritis is the confirmed or suspected cause, or after a total gastrectomy or complete terminal ileal resection.
In these situations, feeling better does not necessarily mean treatment is no longer needed.
Medicine-related deficiency
Some medicines can reduce vitamin B12 levels or interfere with absorption.
Metformin is one example. The Medicines and Healthcare products Regulatory Agency states that reduced B12 levels are a common side effect of metformin and that the risk may increase with higher doses, longer treatment and existing risk factors.
Other medicines, including some acid-reducing treatments, may also be associated with lower vitamin B12 levels.
Do not stop prescribed medicine without medical advice. The appropriate approach may involve monitoring, vitamin B12 replacement or reviewing the medicine with a healthcare professional.
Nitrous oxide use
Recreational nitrous oxide can inactivate vitamin B12 in the body and cause neurological and blood-related effects.
NICE recommends oral or intramuscular vitamin B12 replacement based on clinical judgement and advises stopping recreational nitrous oxide use. The need for ongoing replacement should then be reviewed.
Symptoms involving numbness, weakness, walking difficulties or bladder problems after nitrous oxide use need urgent medical assessment.
Are tablets or injections faster?
The most appropriate treatment depends on the cause and severity of the deficiency.
Vitamin B12 replacement may be given as:
- Oral cyanocobalamin tablets
- Intramuscular hydroxocobalamin injections
- Another treatment selected by a healthcare professional
NHS guidance states that vitamin B12 deficiency anaemia is commonly treated initially with hydroxocobalamin injections every other day for two weeks or until symptoms begin improving. What happens after this depends on the cause and whether neurological symptoms are present.
Injections may be selected when:
- Absorption is impaired
- Neurological symptoms are present
- Symptoms are severe
- Oral treatment is unsuitable
- There are concerns about taking tablets consistently
Oral replacement may be considered when diet is the cause, absorption is not significantly impaired or clinical judgement supports it.
It is not safe to assume that a shop-bought supplement is equivalent to the treatment prescribed for a confirmed deficiency.
How long will vitamin B12 treatment continue?
Treatment can be temporary, long term or lifelong.
Treatment may be temporary when:
- The deficiency was caused by a correctable dietary issue
- The cause has been addressed
- Symptoms have resolved or improved
- A healthcare professional decides replacement is no longer needed
Treatment may continue long term when:
- The cause remains present
- The cause is unknown
- A medicine affecting B12 is still required
- Absorption remains impaired
- Symptoms return when treatment stops
Lifelong treatment may be required when:
- Autoimmune gastritis prevents normal absorption
- The entire stomach has been removed
- The relevant part of the small intestine has been removed
- Another irreversible cause has been identified
NICE advises continuing lifelong intramuscular replacement for irreversible causes even after symptoms have improved or disappeared.
When will you have a follow-up?
NICE recommends an initial follow-up approximately three months after treatment starts, or earlier when symptoms are severe.
People who are pregnant or breastfeeding should generally be followed up after one month. At the appointment, the healthcare professional should ask whether symptoms have improved, worsened or changed.
The follow-up may include checking:
- Whether symptoms have improved
- Whether new symptoms have appeared
- Whether oral treatment is being taken correctly
- Whether the dosage or treatment method needs adjusting
- Whether another diagnosis should be considered
- Whether the underlying cause has been addressed
Follow the schedule advised by your GP or treatment team, as individual circumstances vary.
How do you know if you are recovering?
Signs of improvement may include:
- Less severe tiredness
- Improved ability to complete daily activities
- Reduced weakness
- Fewer episodes of pins and needles
- Improved balance
- Better concentration
- Improvement in a sore or inflamed tongue
- Improvement in blood-related findings where these are monitored
Recovery should be judged using the symptoms that affected you before treatment rather than expecting one universal feeling.
NICE recommends assessing whether symptoms have improved enough that they no longer interfere with normal daily activities.
Why might you not feel better after B12 treatment?
There are several possible reasons.
Recovery needs more time
NICE advises that symptom improvement may take up to three months and complete recovery can take longer.
The cause is still present
Treatment may be less effective when the underlying dietary, absorption, medicine-related or lifestyle cause has not been addressed.
The treatment is not being absorbed
A person with malabsorption may not respond adequately to an ordinary low-dose oral supplement.
The amount is unsuitable
Some over-the-counter supplements may not contain a suitable amount or form for treating deficiency. NICE advises that people using an oral product should choose one containing cyanocobalamin, methylcobalamin or adenosylcobalamin, but treatment decisions should still be based on the cause and clinical circumstances.
Another condition is contributing
Symptoms such as tiredness, weakness and concentration problems can have several causes.
Nerve damage has been present for a long time
Long-standing neurological symptoms may recover slowly and may not always disappear completely.
Contact your healthcare professional rather than changing the amount or frequency of treatment yourself.
Should you start taking vitamin B12 before a blood test?
NICE generally recommends taking diagnostic blood samples before starting vitamin B12 replacement. It also advises telling the healthcare professional about any tablets, injections or patches already being used because these products can affect test results.
However, treatment should not be delayed while waiting for results when suspected deficiency is accompanied by megaloblastic anaemia and neurological symptoms.
Seek medical advice before starting a supplement when you suspect a deficiency, particularly when you have neurological symptoms.
Can an over-the-counter B12 supplement treat a deficiency?
An over-the-counter product may sometimes be used for dietary deficiency, but it should not be assumed to be suitable for every cause.
A shop-bought supplement may not be enough when:
- Absorption is impaired
- Neurological symptoms are present
- The deficiency is severe
- Autoimmune gastritis is suspected
- Previous surgery affects absorption
- A clinician has recommended injections
- The amount or form is unsuitable
A food supplement is not a replacement for diagnosis, prescribed treatment or follow-up.
When should you speak to a GP?
Arrange medical advice when you experience possible symptoms of vitamin B12 deficiency, including:
- Persistent or unexplained tiredness
- Weakness
- Pins and needles
- Numbness
- A sore or red tongue
- Mouth ulcers
- Breathlessness
- Problems with balance
- Memory or concentration changes
- Mood or psychological changes
- Vision problems
Seek prompt medical attention when symptoms are worsening quickly or involve walking difficulties, significant weakness, confusion or bladder and bowel changes.
Early assessment is particularly important because vitamin B12 deficiency can affect the nervous system even when anaemia is absent.
Frequently asked questions
How long does it take to feel better after starting vitamin B12?
Some people may begin to notice improvement within two weeks, while others may take up to three months. Complete disappearance of symptoms can take longer.
How quickly do B12 injections work?
Hydroxocobalamin begins working straight away, but tiredness and other symptoms may take several days or weeks to start improving.
Can vitamin B12 deficiency be cured completely?
Diet-related deficiency may resolve when B12 is replaced and dietary intake improves. Deficiencies caused by irreversible absorption problems usually require ongoing or lifelong replacement.
Why am I still tired after B12 treatment?
Recovery may require more time, or tiredness may have another cause. Speak to a healthcare professional if symptoms are not improving or still affect everyday life.
How long do neurological B12 symptoms take to improve?
Nerve-related symptoms may take months to improve and can recover more slowly than tiredness. Some neurological complications may become permanent when treatment is delayed.
Do B12 levels rise before symptoms improve?
They can. Increasing blood levels does not necessarily mean every symptom will disappear immediately, particularly when the nervous system has been affected.
Will I need B12 treatment for life?
Possibly. Lifelong treatment may be needed when the body cannot absorb B12 because of autoimmune gastritis or certain types of stomach or intestinal surgery.
Can I stop treatment when I feel better?
Do not stop prescribed treatment without professional advice. Symptoms can improve even when the underlying cause remains and replacement is still required.
Can taking extra B12 speed up recovery?
Taking more than advised does not guarantee faster recovery. The correct amount and treatment method depend on the cause and severity of the deficiency.
Can vitamin B12 deficiency return?
Yes. It may return when the cause remains, dietary intake becomes inadequate again or ongoing treatment is stopped.
Final answer
Recovery from vitamin B12 deficiency does not happen at one fixed speed.
Symptoms may begin improving within approximately two weeks, but some people may need up to three months before noticing clear progress. Complete recovery can take longer, especially when the nervous system has been affected or the deficiency was present for a long time.
The cause is just as important as the vitamin B12 level. Dietary deficiency may improve with oral replacement and dietary changes, while absorption-related conditions can require injections and lifelong treatment.
Do not rely on an ordinary food supplement when you have persistent tiredness, pins and needles, weakness, walking difficulties or memory changes. Seek medical assessment so the deficiency and its cause can be properly investigated.