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Cyanocobalamin

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  1. About cyanocobalamin
  2. Key facts
  3. Who can and cannot take cyanocobalamin
  4. How and when to take cyanocobalamin
  5. Side effects of cyanocobalamin
  6. Pregnancy and breastfeeding
  7. Cautions with other medicines
  8. Common questions about cyanocobalamin

1. About cyanocobalamin

Cyanocobalamin is a manufactured version of vitamin B12. It’s used to treat and prevent vitamin B12 deficiency anaemia (when you have low levels of this vitamin in your body).

Your body requires vitamin B12 to make red blood cells. You can get it from your food or supplements, but sometimes there may not be enough vitamins in what you eat. This can happen if you are vegan or you do not eat much meat or dairy products.

Some conditions or treatments can stop you absorbing enough vitamin B12 from the food you eat. These include:

  • pernicious anaemia
  • low stomach acid due to swelling (inflammation) in the lining of the stomach (atrophic gastritis) or certain medicines
  • stomach (gastric) surgery
  • swelling (inflammation) in your intestines because of conditions like Crohn’s disease and coeliac disease
  • an infection in your stomach or intestine

Cyanocobalamin tablets are available on prescription. These come as 50 and 1,000 microgram (μg) tablets.

Cyanocobalamin also comes as injections, but these are generally not available on the NHS. If your doctor prescribes vitamin B12 injections, they will usually give you hydroxocobalamin, another type of vitamin B12.

You can also buy cyanocobalamin B12 supplements from pharmacies, supermarkets and health food shops. These come as tablets, capsules, mouth sprays and drops. They come in different strengths from 10 to 1,000 micrograms (μg).

2. Key facts

  • Cyanocobalamin works by increasing your levels of vitamin B12. You need vitamin B12 to make red blood cells and keep your nervous system healthy.
  • You’ll usually take cyanocobalamin tablets every day to prevent or treat vitamin B12 deficiency. However, you may also need vitamin B12 injections at first to boost your levels.
  • It may take a few weeks before your vitamin B12 levels and symptoms (such as extreme tiredness or lack of energy) start to improve.
  • Some people may be able to stop taking cyanocobalamin when their vitamin B12 blood levels are back to normal.
  • You may have regular blood tests while taking cyanocobalamin, to monitor the levels of vitamin B12 in your blood.

3. Who can and cannot take cyanocobalamin

Most adults and children aged 2 years and over can take cyanocobalamin.

It’s not suitable for everyone. To make sure it’s safe for you, tell your doctor before starting cyanocobalamin if you:

  • have ever had an allergic reaction to cyanocobalamin or any other medicine
  • have an allergy to cobalt

Some cyanocobalamin tablets may not be suitable for people on a vegan diet.

4. How and when to take cyanocobalamin

Dosage

The amount of cyanocobalamin you need depends on the level of vitamin B12 in your blood and why your levels are low. Your doctor or pharmacist will advise you on what dose to take.

The usual dose for:

  • diet-related deficiency is 50 micrograms to 150 micrograms, taken once a day
  • B12 deficiency not caused by your diet is one to two 1,000 microgram tablets, taken once or twice a day – this is usually if you cannot have vitamin B12 injections

In children the doses may be lower.

If you are taking supplements that you have bought, follow the dosage instructions that come with them.

How to take it

Swallow prescribed cyanocobalamin tablets whole with a drink of water. Do not chew or break them.

It’s usually best to take the tablets on an empty stomach. This means at least 2 hours after a meal or snack and at least 30 minutes before you eat again.

For cyanocobalamin supplements that you buy, follow the instructions that come in the packet.

Will my dose go up or down?

To see how well your tablets are working, your doctor may ask you about symptoms such as tiredness and lack of energy. You may also have regular blood tests to monitor the levels of vitamin B12 in your blood.

Your doctor may want to increase or decrease your dose of cyanocobalamin tablets depending on the level of vitamin B12 in your blood.

What if I forget to take it?

If you forget to take cyanocobalamin tablets, take your usual dose as soon as you remember, unless it’s nearly time for your next dose. In this case just leave out the missed dose and take your next one as normal.

Never take more than your usual number of tablets at one time. Never take extra tablets to make up for forgotten ones.

If you forget your tablets often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Taking an extra dose of cyanocobalamin tablets is unlikely to harm you.

Urgent advice: Contact 111 for advice now if:

  • you have taken more than two 1,000 microgram tablets of cyanocobalamin
  • you have taken more than your usual dose and feel sick, vomit or have diarrhoea, or feel worried

Go to 111.nhs.uk or call 111

If you need advice for a child under the age of 5 years, call 111.

5. Side effects of cyanocobalamin

Most people do not have any side effects taking cyanocobalamin tablets.

Serious allergic reaction

In rare cases cyanocobalamin can cause a serious allergic reaction (anaphylaxis).

Immediate action required: Call 999 or go to A&E if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

You could be having a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of cyanocobalamin. For a full list, see the leaflet inside your medicines packet.

Information:

You can report any suspected side effect using the Yellow Card safety scheme.

Visit Yellow Card for further information.

6. Pregnancy and breastfeeding

Cyanocobalamin is generally safe to take in pregnancy and while you are breastfeeding.

You do not usually need to take vitamin B12 supplements when you are pregnant or breastfeeding, unless your doctor has advised you to. You should be able to get all the vitamins you need if you eat meat, fish, eggs, milk and dairy foods.

Cyanocobalamin does pass into breast milk, but it’s not harmful to your baby.

If you notice that your baby is not feeding as well as usual, or if you have any other concerns about your baby, talk to your midwife, health visitor or doctor as soon as possible.

Non-urgent advice: Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

For more information about how vitamin B12 can affect you and your baby during pregnancy read this leaflet on the Best Use of Medicines in Pregnancy (BUMPs) website.

7. Cautions with other medicines

Cyanocobalamin is usually safe to take with other medicines, including painkillers.

Some medicines may reduce the amount of cyanocobalamin you absorb from the tablets or from the food you eat. This will not usually have a noticeable effect. However, tell your doctor or pharmacist if you are taking any of these medicines:

Mixing cyanocobalamin with herbal remedies and supplements

There is very little information about taking herbal remedies and supplements while taking cyanocobalamin.

Important: Medicine safety

Tell your doctor or pharmacist if you're taking any other medicines, including herbal medicines, vitamins or supplements.

8. Common questions about cyanocobalamin

How does cyanocobalamin work?

Cyanocobalamin is a manufactured version of vitamin B12. It works by increasing levels of vitamin B12 in your blood.

You need vitamin B12 to stay healthy. It’s used to make red blood cells and keep your nervous system healthy.

Having enough vitamin B12 allows your body to make red blood cells that work properly to carry oxygen around your body.

If you have been diagnosed with low vitamin B12 levels, taking cyanocobalamin helps reduce symptoms such as tiredness and lack of energy or being short of breath.

Vitamin B12 supplements will only improve symptoms such as tiredness and lack of energy if they are caused by low vitamin B12 levels.

How long does it take to work?

It may take a few weeks before your vitamin B12 levels and symptoms (such as extreme tiredness or lack of energy) start to improve.

If you have hydroxocobalamin injections to boost your vitamin B12 levels at the start of treatment, the cyanocobalamin tablets may start to work within a few days.

How long will I take it for?

Your doctor or pharmacist will advise you how long you need to take cyanocobalamin tablets.

You may be able to stop taking cyanocobalamin when your vitamin B12 blood levels are back to normal.

However, you may need to take it for the rest of your life if your diet does not have enough vitamin B12 or you cannot absorb enough vitamin B12 from your food.

What’s the best vitamin B12 supplement for me?

Vitamin B12 supplements containing cyanocobalamin can be bought as tablets (including chewable, slow-release, and tablets that dissolve under your tongue), capsules, mouth sprays, and drops.

There is no noticeable difference in the amount of vitamin B12 that your body can absorb or use from the different types, so no supplement is more effective than the others.

If you have had stomach or bowel problems or surgery you will not absorb enough vitamin B12 from food or low-dose supplements (10 to 100 micrograms). You will need hydroxocobalamin injections – or high-dose cyanocobalamin tablets (1,000 micrograms) if you cannot have injections.

What will happen if I stop taking cyanocobalamin?

If you stop taking prescribed cyanocobalamin tablets, your vitamin B12 levels may start to go down.

If your levels get too low you may start to get symptoms such as tiredness again.

This may take days, weeks or months to happen because it depends on:

  • what your vitamin B12 levels are
  • how long you have been taking cyanocobalamin
  • how much vitamin B12 you get from your diet

Talk to your doctor or pharmacist if you want to stop taking cyanocobalamin or are bothered by side effects.

Can I drink alcohol with it?

Yes, you can drink alcohol with cyanocobalamin. Alcohol does not affect how this medicine works.

However, drinking too much alcohol on a regular basis can cause folate deficiency anaemia. This is a lack of vitamin B9 (folic acid) and will lead to symptoms such as tiredness coming back.

Is there any food or drink I need to avoid?

You can eat and drink as normal while taking cyanocobalamin. However, it’s best to take cyanocobalamin on an empty stomach, at least 30 minutes before meals or 2 hours after eating.

Will it affect my contraception?

Cyanocobalamin will not stop any contraception working, including the combined pill and emergency contraception.

However, oral contraceptives can reduce the amount of vitamin B12 you absorb from your cyanocobalamin tablets.

Talk to your doctor if you are taking oral contraceptives.

Will it affect my fertility?

There’s no clear evidence to suggest that cyanocobalamin affects fertility in men or women.

Can I drive or ride a bike?

Cyanocobalamin does not usually affect your ability to drive or ride a bike.

What foods can I eat to increase the amount of vitamin B12 in my diet?

You can usually help your vitamin B12 levels by increasing the amount of certain foods you eat. However, this will not help if you have a stomach (gastro-intestinal) problem that means you cannot absorb vitamin B12 from your gut.

If you eat meat, fish, eggs, milk and dairy foods you should get enough vitamin B12 from your diet.

Foods that are good sources of vitamin B12 include:

  • meat (liver, beef)
  • fish (salmon, tuna, haddock)
  • shellfish (muscles, scallops)
  • dairy foods (milk, yoghurt, cheese)
  • eggs

Some foods have vitamin B12 added (look for "fortified" on the label). These include:

  • breakfast cereals and bread
  • soya foods, non-dairy milks and spreads
  • yeast extract or nutritional yeast flakes

If you have a condition that means you cannot absorb enough vitamin B12 from the food you eat, it’s still a good idea to try to eat a healthy, balanced diet with enough vitamins and minerals, including B12.

Page last reviewed: 10 March 2021
Next review due: 10 March 2024