How quickly can you feel the effects of a B12 injection?

How long a B12 injection takes to work depends on why your B12 is low and which symptoms you have. The pharmacist at this Bletchley, Milton Keynes pharmacy hears this question at almost every appointment.

Some people notice more energy within days to a couple of weeks. Nerve symptoms such as pins and needles can take months to improve.

Results vary from person to person. Some symptoms may not fully recover, which is why treating low B12 early matters.

How long does a B12 injection take to work?

It depends on the symptom. Different parts of the body recover at different speeds.

Here is what usually happens:

• Tiredness and low energy: some people feel better within days to a couple of weeks.

• Breathlessness and pale skin: these usually ease as your red blood cells recover over several weeks.

• Sore tongue and mouth ulcers: these often settle within a few weeks.

• Memory, concentration and mood: these can improve over weeks to months.

• Pins and needles, numbness and balance problems: these can take months, and may not fully recover.

Not everyone feels a sudden lift. Some people only notice they are better when they look back a few weeks later.

Why do nerve symptoms take so long to improve?

B12 helps protect and repair your nerves. Once nerves are damaged, they heal slowly.

The longer low B12 goes untreated, the greater the chance that nerve symptoms become permanent. Nerves that have been affected for a long time may only partly recover.

This is why you should not wait and see. If you have tingling, numbness or balance changes, see your GP or the pharmacist promptly.

What does the treatment schedule look like?

The injection is usually hydroxocobalamin 1mg, given into the muscle of your upper arm. It takes seconds.

For confirmed deficiency, treatment often starts with a loading course. That means several injections close together over the first couple of weeks.

Once your levels have improved, injections are spaced further apart. Maintenance injections are usually every 8 to 12 weeks. If you have nerve symptoms, the early phase is usually longer and more frequent.

If you have pernicious anaemia, injections are usually needed long term. This is an autoimmune condition where your body cannot absorb B12 from food.

Will you feel something straight away?

Probably not within minutes. The injection tops up your stores, but your body needs time to rebuild red blood cells and repair nerves.

Side effects are usually mild:

• A sore spot where the needle went in

• A headache

• Feeling sick

• Occasional flushing

Rare allergic reactions can happen. This is one reason the first injection is given somewhere help is close by.

Could your tiredness be something else?

Yes. Tiredness has many causes, and B12 is only one of them.

If you feel better quickly, that is a good sign. If you do not, it may mean something else is going on, such as low iron, thyroid problems or poor sleep.

Low B12 is more likely if you:

• Are vegan or eat little meat, fish, eggs or dairy

• Have pernicious anaemia or Crohn's disease

• Have had stomach or bowel surgery

• Take metformin or acid-reducing medicines such as omeprazole

• Are an older adult

A blood test is the usual way to confirm low B12, and your GP can arrange one. At the appointment, the pharmacist goes through your symptoms, history and medicines to decide whether an injection is appropriate.

Common questions

Does a B12 injection hurt?

It is quick and usually only mildly uncomfortable. Some people have a sore arm for a day or so.

Do you need to be deficient to have a B12 injection?

Injections are for people with confirmed or likely deficiency, or those who cannot absorb B12 from food. They are not a general energy boost.

Are tablets an option instead?

If your low B12 is from diet, tablets often work and cost less. If the cause is poor absorption, tablets are less reliable and injections are the standard treatment. The pharmacist can talk you through which suits you.

Can the NHS do this instead?

Your GP can diagnose low B12 and arrange treatment on the NHS. Some people choose to pay privately for a quicker appointment, a time that suits them, or to get a set schedule sorted without waiting.

Will you need injections for life?

Not always. If low B12 is caused by diet or a medicine, treatment may stop once your levels recover. With pernicious anaemia it is usually lifelong.

Is it safe with my other medicines?

Tell the pharmacist everything you take. If you are pregnant, or have a long-term condition, ask for personalised advice first.

Booking a B12 injection

Kenmakos Medical in Bletchley, Milton Keynes, offers B12 injections for £35 each, with same-week appointments and your next injection booked before you leave.

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