Your doctor may prescribe vitamin B12 injections if you have low levels of B12 in your blood, a condition known as vitamin B12 deficiency. B12 deficiency can result if you don't eat enough of certain foods, particularly meat, poultry and seafood, or if you have an inability to absorb vitamin B12 from food. If your B12 absorption is impaired, you will need to receive injections more frequently than you will if your deficiency is a result of an inadequate diet. According to the Office of Dietary Supplements vitamin B12 is vital to the reaction that creates new DNA in your body. This function is particularly important in keeping your red blood cells healthy. With inadequate vitamin B12, your red blood cells can form incorrectly, leading to a condition known as megaloblastic anemia in which your red blood cells are swollen and ineffective. In addition to its role in DNA synthesis, vitamin B12 is necessary for the proper function of your nervous system. The daily recommended intake of vitamin B12 for adults is 2.4 mcg, and you can meet this need through supplementation or by eating a variety of animal products, including milk, meat and seafood.
Vitamin B12 deficiency occurs in 1.5 to 15 percent of the general public. According to a 2008 article in the journal "Blood," it may take 2 to 5 years for clinical symptoms of vitamin B12 deficiency to appear in people with malabsorption disorders such as pernicious anemia or sprue. If you don't eat meat, as in the case of a vegan diet, it may take more than 10 years before signs of deficiency appear. Deficiency is slow to develop because your body is able to store a large amount of vitamin B12 in the liver and other tissues. Symptoms of vitamin B12 deficiency include shakiness, inability to control bodily actions and neurological changes including psychosis or changes in mood. Doctors typically administer injections of vitamin B12 in doses of 1000 mcg. This amount of vitamin B12 corrects the physiological consequences of deficiency and also helps build up body stores of the vitamin. Of this 1000 mcg dose, your body retains approximately 150 mcg or roughly 15 percent. You retain a higher percentage of smaller doses, but the overall amount of vitamin B12 obtained from smaller doses is still less than that stored from a 1000-mcg injection.
Owing to your body's ability to store large amounts of vitamin B12, injections may be infrequent once your deficiency is resolved. If you cannot absorb vitamin B12 from food, Dr. Ralph Caramel, author of a 2008 article on vitamin B12 in the journal "Blood," suggests an initial injection cycle of 8 to 10 administrations over the first two to three months, then injections once a month thereafter. If you have low vitamin B12 levels that are due to improper intake, you will need fewer injections, provided you begin to eat foods rich in vitamin B12 more often. Always consult with your doctor or pharmacist regarding how often you should be receiving vitamin B12 injections. According to the Office of Dietary Supplements, overdosing on vitamin B12 is difficult and no known adverse health effects are associated with high vitamin B12 intakes from either food or supplements. Vitamin B12 can interact with certain medications, however. Check with your doctor or pharmacist about possible interactions these injections may have with other medications you are taking.
Though very rare, allergic reactions to vitamin B12 injections have occurred, and switching to an oral preparation of vitamin B12 may help prevent the reaction or reduce its severity. Why Are the B12 Injections Not Working? Are There Advantages of Sublingual Vitamin B12? Does Sublingual B12 Really Work? Vitamin B12 by Subcutaneous Injection What Is the Normal Intramuscular Dose of Vitamin B12? Can You Get Vitamin B12 Anemia If You Had Your Gallbladder Removed? How is a B12 Injection Given? Alcohol's Effects on B-12 Absorption Taking Vitamins With Food Vs. When Will I Feel Better With B12? The Best-Absorbed B12 Supplement How to Test for Vitamin and Mineral Deficiencies Taking B6 & B12 to Lose WeightA lack of vitamin B12 (B12 deficiency) is one cause of anaemia. Pernicious anaemia is a condition where vitamin B12 cannot be absorbed into your body. It is the most common cause of vitamin B12 deficiency in the UK. Vitamin B12 deficiency can easily be treated by regular injections of vitamin B12.
Blood is made up of a fluid called plasma which contains:Red blood cells are made in the bone marrow and millions are released into the bloodstream each day. A constant new supply of red blood cells is needed to replace old cells that break down. Red blood cells contain a chemical called haemoglobin. Haemoglobin binds to oxygen and takes oxygen from the lungs to all parts of the body. To make red blood cells and haemoglobin constantly you need a healthy bone marrow and nutrients such as iron and certain vitamins, including vitamin B12, which we get from food.In either case, a reduced amount of oxygen is carried around in the bloodstream. There are various different causes of anaemia such as lack of iron or certain vitamins.Vitamin B12 is essential for life. It is needed to make new cells in the body such as the many new red blood cells which are made every day. Vitamin B12 is found in meat, fish, eggs and milk - but not in fruit or vegetables. A normal balanced diet contains enough vitamin B12.
A lack of vitamin B12 leads to anaemia and sometimes to other problems.These are caused by the reduced amount of oxygen in the body.Cells in other parts of the body may be affected if you lack vitamin B12. Other symptoms that may occur include a sore mouth and tongue.If left untreated, problems with nerves and psychological problems can develop. Psychological problems may include depression, confusion, difficulty with memory or even dementia. Nerve problems may include numbness, pins and needles, vision changes and unsteadiness.Normally, when you eat foods with vitamin B12, the vitamin combines with a protein called intrinsic factor in the stomach. The combined vitamin B12/intrinsic factor is then absorbed into the body further down the gut at the end of the small intestine. (Intrinsic factor is made by cells in the lining of the stomach and is needed for vitamin B12 to be absorbed.)Pernicious anaemia is the most common cause of B12 deficiency in the UK. It is classed as an autoimmune disease.
The immune system normally makes antibodies to attack bacteria, viruses and other germs. If you have an autoimmune disease, the immune system makes antibodies against certain tissues of your body. If you have pernicious anaemia, antibodies are formed against your intrinsic factor, or against the cells in your stomach which make intrinsic factor. This stops intrinsic factor from attaching to vitamin B12 and so the vitamin cannot be absorbed into your body. It is thought that something triggers the immune system to make antibodies against intrinsic factor. The trigger is not known.Pernicious anaemia usually develops over the age of 50. Women are more commonly affected than men and it tends to run in families. It occurs more commonly in people who have other autoimmune diseases. For example, thyroid diseases, Addison's disease and vitiligo (a condition where white patches develop on skin). The antibodies which cause pernicious anaemia can be detected by a blood test to confirm the diagnosis.
Various problems of the stomach or gut can be a cause of vitamin B12 deficiency. They are all uncommon causes. They include:Certain medicines used for other conditions may affect the absorbtion of vitamin B12. The most common example is metformin which is a medicine often used for diabetes. Other medicines include colchicine, neomycin and some anticonvulsants used to treat epilepsy.Note: long-term use of medicines that affect stomach acid production, such as H2 blockers and proton pump inhibitors, can worsen vitamin B12 deficiency. This is because stomach acid is needed to release vitamin B12 bound to proteins in food. However, such medicines are not causes of vitamin B12 deficiency.It is unusual to lack vitamin B12 if you eat a normal balanced diet. Strict vegans who take no animal or dairy produce may not eat enough vitamin B12. Some foods are fortified with vitamin B12 - for example, some soy products, some breakfast cereals and some breads.The level of vitamin B12 can be measured by a blood test.
Further tests are then needed to find out the cause of the vitamin B12 deficiency.These further tests include blood tests for intrinsic factor antibodies and gastric parietal cell antibodies. These blood tests help to find out whether you have pernicious anaemia.You will need vitamin B12 injections. The injections are usually given frequently at the start of treatment. This quickly builds up the body's store of vitamin B12. Vitamin B12 is stored in the liver. Once a store of vitamin B12 has built up, this can supply the body's needs for several months. An injection is then only usually needed every two to three months to top up the supply.The recommended dose if you do not have any nerve problems caused by pernicious anaemia is initially an injection three times a week for two weeks and then one injection every three months.The recommended dose if you do have any nerve problems caused by pernicious anaemia is initially an injection every other day until there is no further improvement in your symptoms, then one injection every two months.
There is a small group of people with vitamin B12 deficiency who report that their symptoms come back (recur) before the usual three-monthly treatment dose. Therefore, some people have injections more often than three-monthly. However, this is not common and is best discussed with your doctor.If you have pernicious anaemia the injections are needed for life. Apart from the discomfort of having an injection, you should have no side-effects from the treatment. The injections are simply replacing a vitamin that you need. If the cause of your lack of vitamin B12 is diet-related rather than due to pernicious anaemia then treatment may be different. That is, after the initial treatment with injections of vitamin B12, dietary supplements of vitamin B12 (cyanocobalamin tablets) may be advised instead of injections. Alternatively, injections of vitamin B12 twice a year may be recommended.See also separate leaflet called Diets Suitable for People with Anaemia.The symptoms of anaemia usually improve quickly once treatment has begun.