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).

• 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.

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.

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.

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).

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.

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.

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:

• metformin for diabetes
• antacids like Gaviscon
• H2 blockers like ranitidine , cimetidine, famotidine, nizatidine
• proton pump inhibitors (PPIs) like lansoprazole, omeprazole, pantoprazole or rabeprazole
• antibiotics such as chloramphenicol and neomycin
• oral contraceptives such as the combined pill

Mixing cyanocobalamin with herbal remedies and supplements

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