If Addison's disease is suspected, blood tests will be carried out to measure the levels of sodium, potassium and cortisol in your body. A low sodium, high potassium or low cortisol level may indicate Addison's disease.
You may need to see a hospital hormone specialist (endocrinologist) for your blood to be tested for the following:
- a low level of the hormone aldosterone
- a high level of adrenocorticotrophic hormone (ACTH)
- a low level of glucose (sugar used for energy)
- positive adrenal antibodies (antibodies designed to attack the adrenal gland)
Any of the above could be a sign of Addison's disease.
Synacthen stimulation test
If cortisol in your blood is low or your symptoms strongly suggest Addison's disease, you'll need to have a synacthen stimulation test to confirm the diagnosis.
Your GP may refer you to an endocrinology unit (a unit that specialises in the study of hormones) for the test. How urgent the referral is will depend on how severe your symptoms are.
Synacthen is a man-made (synthetic) copy of the adrenocorticotrophic hormone (ACTH). ACTH is naturally produced by the pituitary gland (a pea-sized gland below the brain) to encourage the adrenal glands to release cortisol and aldosterone.
When synacthen is given, the adrenal glands should respond in the same way as they would to ACTH by releasing cortisol and other steroid hormones into the blood.
A blood sample will be taken and tested for cortisol before an injection of synacthen is given into your arm. Further blood samples will be taken to measure cortisol after 30 minutes and after 60 minutes.
If the ACTH level is high but the cortisol and aldosterone levels are low, it's usually confirmation of Addison's disease.
Thyroid function test
Your thyroid gland may also be tested to see if it's working properly.
Your thyroid gland is found in your neck. It produces hormones that control your body's growth and metabolism.
People with Addison's disease often have an underactive thyroid gland (hypothyroidism), where the thyroid gland does not produce enough hormones.
By testing the levels of certain hormones in your blood, your endocrinologist (a specialist in hormone conditions) can determine whether you have hypothyroidism.
Diagnosis during an adrenal crisis
If Addison's disease is left untreated, it eventually leads to an adrenal crisis. This is where the symptoms of Addison's disease appear quickly and severely.
During an adrenal crisis, there's not enough time to perform a synacthen stimulation test to confirm Addison's disease.
If possible, blood will be taken and tested for any of the abnormalities listed above. While you're waiting for the results, treatment may be started with steroid injections, and fluids containing salt and glucose.
Read more about treating Addison's disease.
If you're diagnosed with Addison's disease and have a bus, coach or lorry licence, it's your legal obligation to inform the Driver and Vehicle Licensing Agency (DVLA).
Read about driving and Addison's disease on the GOV.UK website.