Type 1 diabetes and other autoimmune conditions: coeliac, thyroid and Addison's disease

The NHS explains that pernicious anaemia and Addison's disease are autoimmune conditions in which the immune system attacks healthy cells, and that coeliac disease is an autoimmune condition in which the immune system attacks tissue when you eat gluten.

Diabetes UK says that people with type 1 diabetes are more at risk of other autoimmune conditions such as coeliac disease or thyroid disease. The NHS says the link runs the other way too: you are more likely to get type 1 diabetes if you have other autoimmune conditions or if others in your family have type 1 diabetes or other autoimmune conditions.

Some clinicians use the name autoimmune polyendocrine syndrome for particular patterns in which several hormone glands are affected by autoimmunity. The NHS, NICE and Diabetes UK pages used for this guide do not use that label, and this guide does not rely on it. What matters in practice is being aware that more than one autoimmune condition can develop over time, and that checking for them is part of routine diabetes care.

The conditions below are those named in the NHS, NICE and Diabetes UK pages read for this guide. None of them is inevitable, and most people with type 1 diabetes will have one condition only.

The NHS lists the common symptoms of an underactive thyroid as extreme tiredness, feeling cold, weight gain, constipation, difficulty concentrating, low mood, dry skin and hair, a croaky voice and irregular or heavy periods, and says symptoms usually develop slowly and get worse over time. It also says that in the UK the main cause of an underactive thyroid is an autoimmune condition called Hashimoto's disease.

An underactive thyroid is usually treated with levothyroxine tablets, which the NHS says you will usually need to take for the rest of your life, with regular blood tests to check the dose is right. NICE recommends measuring TSH at the annual review of adults with type 1 diabetes, and the NHS says the annual diabetes check-up includes checking the thyroid, so a problem is often picked up before you notice symptoms.

The NHS says coeliac disease can cause diarrhoea, stomach aches, bloating, indigestion, constipation, tiredness, unintentional weight loss and an itchy rash, and that some people have few gut symptoms. It lists type 1 diabetes among the conditions that increase the risk of coeliac disease. Treatment is a gluten-free diet, which the NHS says should control symptoms and prevent long-term complications, and it recommends changing diet even if symptoms are mild.

NICE says that in adults with type 1 diabetes who have unexplained weight loss, coeliac disease should be assessed, and refers readers to its separate coeliac guideline for testing. The NHS also says first-degree relatives of people with coeliac disease should be tested.

The NHS describes Addison's disease as a rare condition in which the adrenal glands do not work properly, and says the most common cause is the immune system mistakenly attacking and damaging the adrenal glands. Symptoms include extreme tiredness, darker patches of skin, loss of appetite and weight loss, tummy pain, feeling or being sick, cravings for salty foods, dizziness when standing up, muscle weakness and cramps, thirst and needing to pee a lot, and anxiety or depression.

The NHS says there is no cure, but the main treatment is steroid medicine to replace the missing hormones, usually for life, with extra doses needed when you are unwell, about to have surgery or under stress. Adrenal crisis is a medical emergency in which symptoms get worse very quickly, and the NHS says to call 999 if you have Addison's disease and your symptoms suddenly worsen.

The NHS describes pernicious anaemia as an autoimmune condition that affects the stomach. It says the exact cause is unknown but it is more common in women around 60 years of age, people with a family history and those with another autoimmune condition, such as Addison's disease or vitiligo. NICE specifically names pernicious anaemia, alongside Addison's disease, as a condition to be alert to in adults with type 1 diabetes. Persistent tiredness and other new symptoms should therefore be mentioned to a clinician rather than put down to diabetes.

Persistent tiredness, unexplained weight loss, new gut symptoms, feeling the cold, a new rash or repeated unexplained low blood sugars should be mentioned to your GP or diabetes team. The NHS says that for type 1 diabetes you should ask for an urgent GP appointment or get help from NHS 111 if you think you or your child may have type 1 diabetes, and call 999 or go to A&E if symptoms worsen quickly, you have stomach pain, diarrhoea or feel sick, feel sleepy or confused, or are breathing faster and more deeply than usual, because these can be signs of diabetic ketoacidosis.

The NHS says your diabetes care plan includes advice on what to do when you are ill, called sick day rules, and on how to recognise and treat low and high blood glucose. Follow it, and ask your diabetes team if you are unsure.

On the NHS, the annual diabetes review is the usual point at which thyroid blood tests and other checks are done, and a GP or diabetes specialist team can arrange tests for coeliac disease, adrenal function or vitamin B12. Private blood tests are available, but results are best reviewed with your diabetes team because they know how your diabetes treatment, medicines and symptoms fit together.