Autoimmune gastritis: symptoms, vitamin B12 deficiency and treatment

Gastritis means that the lining of the stomach is irritated or inflamed. The NHS lists several causes: infection with Helicobacter pylori bacteria, anti-inflammatory painkillers and aspirin, drinking too much alcohol, being very stressed and unwell, and having stomach surgery such as gastric bypass. It adds that gastritis can also be caused by a problem with the immune system, where it attacks the lining of the stomach. That immune-driven form is what is usually called autoimmune gastritis.

An autoimmune condition means the immune system, which normally defends against infection, mistakenly attacks the body’s own healthy cells. In autoimmune gastritis the target is the stomach lining, including the cells that make intrinsic factor, a protein needed to absorb vitamin B12. The NHS pages used for this guide describe this process under the name pernicious anaemia and do not use the term autoimmune gastritis, so the two are closely related rather than interchangeable. Pernicious anaemia is the anaemia and deficiency that follows when B12 cannot be absorbed.

The NHS explains that vitamin B12 combines with intrinsic factor in the stomach, and this mix is then absorbed in part of the gut called the distal ileum. When the immune system attacks the cells that produce intrinsic factor, the body cannot absorb B12, even if the diet contains plenty of it.

The body holds stores of vitamin B12 that the NHS says can last around 2 to 5 years without being replenished, so problems can take a long time to appear. That is one reason the condition is often found late, after years of slowly building deficiency.

The NHS says the exact cause of pernicious anaemia is unknown, but it is more common in women around 60 years of age, in people with a family history of the condition, and in those with another autoimmune condition such as Addison’s disease or vitiligo.

The symptoms usually develop gradually and can worsen if the condition goes untreated. The NHS lists symptoms of vitamin B12 deficiency anaemia that include:

• extreme tiredness, weakness and a lack of energy

• shortness of breath, palpitations and headaches

• a sore, red tongue, sometimes with mouth ulcers

• indigestion, loss of appetite and diarrhoea

• problems with vision

• problems with memory, understanding and judgement

Vitamin B12 deficiency can also affect the brain and nervous system, and the NHS notes that some of these symptoms can occur without anaemia. They include numbness and pins and needles, muscle weakness, problems with balance and coordination, incontinence, and psychological problems ranging from mild depression or anxiety to confusion and dementia.

The NHS stresses that although many symptoms improve with treatment, some can be irreversible, and the longer the condition goes untreated the higher the chance of permanent damage. Complications it lists include problems with the nervous system, temporary infertility, heart conditions and pregnancy complications, and adults with severe anaemia are at risk of heart failure.

The NHS says symptoms of gastritis include tummy pain, indigestion, feeling full and bloated, nausea, vomiting and not feeling as hungry as usual. Most are not serious, but the NHS advises seeing a GP if tummy pain or indigestion lasts longer than 1 week, or if it is getting worse or keeps coming back.

It advises asking for an urgent GP appointment or calling NHS 111 if you also have loss of appetite, feel full after a very small meal, have lost weight without trying, feel a lump in your tummy, find swallowing painful or difficult, or keep being sick. Call 999 or go to A&E if you are vomiting bright red blood or your vomit looks like ground coffee, your poo is black, sticky and extremely smelly, or you have severe tummy or chest pain that started suddenly.

The NHS says B12 and folate deficiency can often be diagnosed from your symptoms and a blood test. For gastritis, a GP may arrange a breath test for H. pylori, a test on a poo sample, or a blood test, to find the cause. If gastritis is not getting better or causes severe symptoms, a GP might refer you to a specialist stomach doctor (gastroenterologist), who may arrange a gastroscopy to look inside the stomach.

A normal blood B12 level does not always settle the question. The NHS describes a functional form of B12 deficiency in which problems occur despite apparently normal blood levels because of a problem with transport proteins, so persistent symptoms deserve a conversation with your GP even if a first result is reassuring.

The NHS says B12 deficiency anaemia is usually treated with injections of hydroxocobalamin, given every other day at first by a GP or nurse. What happens next depends on the cause.

The NHS says a blood test is often carried out around 7 to 10 days after starting treatment to check haemoglobin and the number of immature red blood cells, and another after about 8 weeks to confirm treatment has been successful. Most people who have had B12 deficiency will not need further monitoring unless their symptoms return or treatment is ineffective.

If gastritis is part of the picture, the NHS says treatment depends on the cause and can include medicines to control stomach acid such as antacids, proton pump inhibitors or alginates, and reviewing anti-inflammatory painkillers and alcohol. It also notes that untreated gastritis can get worse and cause a stomach ulcer. The sources used for this guide do not describe longer-term stomach surveillance, so ask your gastroenterologist whether any follow-up scopes apply to you.

Folic acid is sometimes also needed, but the NHS says your GP will check B12 levels first because folic acid can improve symptoms so much that it masks an underlying B12 deficiency.

Testing, B12 injections and specialist referral are available through the NHS, normally via your GP surgery, where a nurse often gives the injections. Some people choose a private gastroenterologist for a faster appointment or gastroscopy. The investigations are the same, so the main differences are waiting time and choice of clinician. Whichever route you use, make sure your GP knows about any private results and who is responsible for your regular injections.