Key points about vitamin B12 deficiency anemia
Without enough red blood cells, your tissues and organs don’t get enough oxygen. Without enough oxygen, your body can’t work as well. Symptoms include weak muscles, numbness, trouble walking, nausea, weight loss, irritability, fatigue, and increased heart rate.

Vitamin B12 does a lot of things for your body. It helps make your DNA and your red blood cells, for example.
Since your body doesn't make vitamin B12, you have to get it from animal-based foods or from supplements. And you should do that on a regular basis. While B12 is stored in the liver for up to 5 years, you can eventually become deficient if your diet doesn't help maintain the levels.
How Much Should You Get?
The answer depends on things including your age, your eating habits and medical conditions, and what medications you take.
The average recommended daily amounts, measured in micrograms (mcg), vary by age:
Infants up to age 6 months: 0.4 mcg
Babies ages 7-12 months: 0.5 mcg
Children ages 1-3 years: 0.9 mcg
Kids ages 4-8 years: 1.2 mcg
Children ages 9-13 years: 1.8 mcg
Teens ages 14-18: 2.4 mcg (2.6 mcg per day if pregnant and 2.8 mcg per day if breastfeeding)
Adults: 2.4 mcg (2.6 mcg per day if pregnant and 2.8 mcg per day if breastfeeding)

vitamin b12 deficiency causes
Diet. Some people can develop a vitamin B12 deficiency as a result of not getting enough vitamin B12 from their diet. A diet that includes meat, fish and dairy products usually provides enough vitamin B12, but people who do not regularly eat these foods can become deficient.

vitamin b12 deficiency symptoms
rapid breathing or shortness of breath.
headaches.
indigestion.
loss of appetite.
palpitations.
problems with your vision.
feeling weak or tired.
diarrhoea.

vitamin b12 deficiency treatment
Vitamin B12 deficiency anaemia is usually treated with injections of vitamin B12, called hydroxocobalamin. At first, you'll have these injections every other day for 2 weeks or until your symptoms have started improving. Your GP or nurse will give the injections.
Vitamin b12 deficiency causes
Vitamin B12 deficiency happens if you are not eating enough vitamin B12 or your body is not absorbing the vitamin B12 you consume properly. Situations or conditions that can cause vitamin B12 deficiency include:
Lack of vitamin B12 in your diet: People who don’t eat enough foods that naturally have vitamin B12 or don’t eat foods fortified with vitamin B12 can develop vitamin B12 deficiency.
Gastritis: Gastritis is inflammation of the stomach lining, and it’s a common cause of vitamin B12 deficiency. It can cause vitamin B12 deficiency due to a lack of hydrochloric acid in your stomach, which is needed for vitamin B12 absorption.
Pernicious anemia: People who have pernicious anemia, a rare medical condition, are not able to make intrinsic factor, a protein made by your stomach. You need intrinsic factor so that your body can absorb B12 vitamin. People with pernicious anemia have a B12 vitamin deficiency.
Digestive diseases: Diseases that affect the digestive system, like Crohn’s disease and celiac disease, can prevent your body from fully absorbing vitamin B12.
Surgery: People who have gastrointestinal surgery, such as a gastric bypass (weight loss surgery), can have difficulty absorbing vitamin B12.
Alcohol use disorder: This condition can damage your digestive system and cause vitamin B12 deficiency.
Transcobalamin II deficiency: This is a rare genetic disorder that impairs the transport of vitamin B12 (also known as cobalamin) within the body.
Symptoms of Vitamin B12 Deficiency
If you have vitamin B12 deficiency, you could become anemic. A mild deficiency may cause no symptoms. But if untreated, it may lead to symptoms such as:
- Weakness, tiredness, or lightheadedness
- 2. Heart palpitations and shortness of breath
- Pale skin
- A smooth tongue
- Constipation, diarrhea, loss of appetite, or gas
- Nerve problems like numbness or tingling, muscle weakness, and problems walking
- Vision loss
- Mental problems like depression, memory loss, or behavioral changes
How is vitamin B12 Deficiency Treated?
Vitamin B12 deficiency can be treated with vitamin B12. It is often treated with cyanocobalamin, a man-made form of vitamin B12. Depending on the cause of the deficiency, the person may only have to be treated until their vitamin B12 levels are back to normal, or they may have to take vitamin B12 therapy for the rest of their life. Options for vitamin B12 treatment include:
Vitamin B12 oral medication.
Vitamin B12 intramuscular injections (a shot that goes into the muscle).
Vitamin B12 nasal gel.
Vitamin B12 nasal spray.
PREVENTION
What are the risk factors for vitamin B12 deficiency?
A person is more likely to develop vitamin B12 deficiency if they have one or more of the following risk factors:
Being older than 75 years: Elderly people are more at risk for developing vitamin B12 deficiency because their bodies are often unable to fully absorb vitamin B12.
Having a digestive system disorder: Digestive disorders such as celiac disease and Crohn’s disease can make it more difficult for your body to absorb vitamin B12.
Following a strict vegan or vegetarian diet: Vitamin B12 is only naturally found in animal products such as meat and dairy. Because of this, people who eat a vegan or vegetarian diet are more likely to have a vitamin B12 deficiency if they aren’t eating enough fortified foods with vitamin B12.
Taking certain medications: Certain medications can cause low levels of vitamin B12 in your body, including metformin (a drug used to manage diabetes), proton pump inhibitors (PPIs are used to treat GERD and peptic ulcers), histamine H2 blockers (a medicine used to reduce the amount of acid your stomach makes) and oral birth control pills (oral contraceptives).
Having Sjögren’s syndrome. People with Sjögren’s syndrome are over six times more likely to have vitamin B12 deficiency.
Drinking excessive amounts of alcohol: Chronic alcoholism can damage your digestive system and cause vitamin B12 deficiency.
Change Your Life
For most people, treatment resolves the problem. But, any nerve damage that happened due to the deficiency could be permanent.