How the dose is calculated
Hydrocortisone is dosed per single IV bolus by weight — the dose and cap depend on the indication, since adrenal crisis and severe asthma/anaphylaxis use different weight-based targets.
Typical dosing by indication
| Indication | Dose | Max single dose |
|---|---|---|
| Adrenal crisis / stress dose | 2 mg/kg IV bolus | 100 mg |
| Severe asthma / anaphylaxis adjunct | 4 mg/kg IV | 200 mg |
In anaphylaxis, hydrocortisone is an adjunct given after adrenaline — it does not treat the acute reaction and has a delayed onset of action, so it should never delay or substitute for IM adrenaline.
Clinical use
- First-line replacement for suspected or confirmed adrenal crisis (e.g. known adrenal insufficiency with acute illness, sepsis with refractory hypotension on steroids).
- Used as an adjunct in severe asthma exacerbations and anaphylaxis to reduce the risk of a biphasic/late-phase reaction — but its onset takes hours, so it never replaces adrenaline as first-line anaphylaxis treatment.
- Stress-dose steroid coverage is also considered peri-operatively in patients on long-term corticosteroids or with known adrenal suppression.
Frequently asked questions
What is hydrocortisone used for in an emergency?
Adrenal crisis (as urgent steroid replacement) and as an adjunct in severe asthma and anaphylaxis to help prevent a delayed or biphasic reaction.
Does hydrocortisone treat anaphylaxis on its own?
No — it has a delayed onset of action (hours) and is only an adjunct. Intramuscular adrenaline is always the first-line, time-critical treatment for anaphylaxis; hydrocortisone should never delay it.
Why does the dose differ between adrenal crisis and asthma/anaphylaxis?
Adrenal crisis dosing aims to replace physiological cortisol output at a stress level, while asthma/anaphylaxis dosing uses a higher anti-inflammatory target — the two indications have different evidence-based dosing conventions.
References
- Bornstein SR, et al. Diagnosis and Treatment of Primary Adrenal Insufficiency: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2016;101:364-389.
- Resuscitation Council UK. Emergency Treatment of Anaphylactic Reactions.