Sick Day Rules For Adrenal Insufficiency

Kasi Subbiah

Sep 20

4 min read

Updated: Sep 28

During illness, injury, fever, vomiting, diarrhoea, or severe physical stress, the body needs extra hydrocortisone.

Most glands are polite. They do their work quietly in the background and avoid drama. The adrenal glands are usually like that too: small, triangular, and rather understated. But when the body is under stress, they suddenly become very important.

During illness, injury, fever, vomiting, diarrhoea, or severe physical stress, the body normally releases extra cortisol. Cortisol is one of the body's main keep going hormones. It helps maintain blood pressure, blood sugar, salt balance, energy supply, and the body's response to inflammation.

In adrenal insufficiency, that emergency reserve is missing or unreliable. This applies to people with primary adrenal insufficiency, such as Addison's disease; secondary adrenal insufficiency, where the pituitary does not send enough ACTH signal to the adrenal glands; and steroid-induced adrenal insufficiency, where the body's own cortisol production has been suppressed by long-term steroid treatment.

The principle is simple: when your body would normally make more cortisol, you need to take more steroid replacement. That is the heart of sick day rules.

Why sick day rules matter

On a normal day, steroid replacement is designed to copy the body's usual cortisol production. It is not meant to cover a chest infection, food poisoning, a high fever, a broken bone, or a hospital admission.

Think of daily hydrocortisone or prednisolone as the background heating. Most days, that is enough. But illness is a cold snap. The system needs turning up, and occasionally it needs emergency support.

Without enough cortisol during illness, patients can develop adrenal crisis. This can cause severe weakness, vomiting, dehydration, low blood pressure, confusion, collapse, low blood sugar, and abnormal blood salts. It is not a wait and see situation. The body is asking for cortisol now, not after a committee meeting.

Who needs sick day rules

Primary adrenal insufficiency, including Addison's disease or bilateral adrenal removal.
Secondary adrenal insufficiency due to pituitary or hypothalamic disease.
Congenital adrenal hyperplasia treated with steroid replacement.
Steroid-induced adrenal insufficiency after long-term oral steroids, high-dose inhaled steroids, repeated steroid injections, or other steroid exposure.
Any condition where a clinician has said the patient is steroid-dependent or at risk of adrenal crisis.

The exact replacement regimen may differ, but the safety principle is shared: during significant illness, steroid cover must rise quickly.

Mild illness when tablets are staying down

If there is a mild cold without fever and the patient feels generally well, a dose change may not be needed. A runny nose alone does not usually deserve a red carpet and a steroid parade.

But if there is fever, flu-like illness, significant infection, COVID-like illness, worsening chest or urine infection, or the patient feels clearly unwell, most guidance recommends increasing glucocorticoid dose temporarily.

This should be personalised by the endocrinology team, especially if usual doses are higher, lower, or unusual.

Vomiting or diarrhoea changes the rules

Vomiting is different because tablets may not be absorbed. If tablets are not staying in, the steroid is not reliably getting in.

If vomiting continues, or tablets cannot be kept down, the patient should use their emergency hydrocortisone injection and seek urgent medical help. Severe diarrhoea, especially with dehydration, dizziness, abdominal pain, fever, or inability to drink properly, also needs urgent attention.

When to use the emergency hydrocortisone injection

The patient cannot keep steroid tablets down because of vomiting.
There is repeated vomiting or severe diarrhoea.
The patient is very drowsy, confused, faint, collapsing, or too unwell to manage safely with tablets.
There is severe injury, major physical stress, or suspected adrenal crisis.
Emergency services or the endocrine team advise injection.

After using the injection, emergency medical care is still needed. The injection buys time; it is not the end of the story. Fluids, blood pressure support, glucose, salts, infection treatment, and further hydrocortisone may be needed.

What about fludrocortisone

People with primary adrenal insufficiency often take fludrocortisone because the adrenal glands are not making enough aldosterone, the hormone that helps regulate salt and water balance.

During illness, dehydration becomes more dangerous. Vomiting, diarrhoea, sweating and fever can all reduce fluid volume. This is why patients with primary adrenal insufficiency may need closer attention to hydration and salt intake. During high-dose hydrocortisone treatment in hospital, hydrocortisone itself has some mineralocorticoid effect, so fludrocortisone dosing may be reviewed by clinicians.

Steroid-induced adrenal insufficiency

Steroid-induced adrenal insufficiency deserves special mention because patients may not always realise they are at risk. Long-term steroid treatment can quieten the hypothalamic-pituitary-adrenal axis. The brain notices there is steroid in the system and reduces ACTH signalling. The adrenal glands, receiving fewer instructions, may temporarily reduce their own cortisol production.

This can happen after prolonged oral prednisolone, but also in selected patients after high-dose inhaled steroids, repeated steroid injections, potent topical steroids, or interacting medicines. The risk depends on dose, duration, route, individual susceptibility, and whether recovery has been confirmed.

When to seek urgent help

Repeated vomiting or diarrhoea.
Dizziness, fainting, collapse, or severe weakness.
Confusion, marked drowsiness, or difficulty staying awake.
Severe abdominal pain.
High fever or symptoms of sepsis.
Low blood pressure, cold clammy skin, or feeling shut down.
Inability to take or absorb oral steroid.
Need for emergency injection.

If in doubt, treat first and seek help. Adrenal crisis is one of those rare medical situations where hesitation can be more dangerous than being overcautious.

Practical sick day checklist

Steroid emergency card.
Medical alert jewellery or phone medical ID.
In-date emergency hydrocortisone injection kit.
Written sick day rules.
Spare hydrocortisone or prednisolone.
A plan for who can give the injection.
Clear instructions for family, friends or colleagues.
Contact details for the endocrine team.
A low threshold to call 999 if severely unwell.

Closing thought

Sick day rules are not meant to make life feel fragile. They are the opposite. They are a way of making adrenal insufficiency predictable when the body is under pressure.

The aim is not to panic at every sniffle. It is to recognise the moments when the body would normally raise cortisol, and to replace that missing response early. A small gland may have gone quiet, but the plan does not have to.