What Happens If You Miss a Hydrocortisone Dose for CAH?

If you accidentally miss a single routine dose of your daily hydrocortisone on an otherwise healthy day, it may not cause an immediate medical emergency, but the risk varies from person to person ^[1]. Hydrocortisone replaces the cortisol your body does not make enough of and helps control the excess production of other adrenal hormones ^[1][2]. Because consistency is critical to managing Classic Congenital Adrenal Hyperplasia (CAH), it is important to know exactly what to do when a dose is missed or delayed.

Because hydrocortisone is often taken two or three times a day, there is no universal cutoff for when a late dose is “too late” to take ^[3]. You must ask your doctor or pharmacist for a specific missed-dose plan. However, general safety principles state that you should not change your medication schedule or double your next routine dose on your own to “catch up” without medical advice ^[4][2].

Quick Decision Guide: What to Do

Every patient with the simple virilizing form of CAH should have a written, individualized care plan. Below is general guidance on how different scenarios are typically handled:

• You are healthy but missed a dose: Check your written plan or contact your pharmacy. Do not automatically double your next dose unless instructed ^[4].
• You are sick or have a fever: Missing a dose while ill is dangerous. You must follow your written “sick-day” or “stress-dosing” plan (which often involves taking double or triple the normal dose) ^[3].
• You vomited immediately after taking a pill: Check your written plan; doctors often recommend repeating the oral dose once if it was thrown up immediately ^[3][4].
• You have persistent vomiting or diarrhea: This is a medical emergency. If you cannot keep fluids or medication down, oral pills will not work. You must administer your emergency injectable hydrocortisone and seek urgent medical care ^[3][5].

Tip for preventing missed doses: Use a daily pillbox, set recurring phone alarms, always keep a backup medication supply with you, and wear medical-alert identification so others know about your condition in an emergency.

The Short-Term Impact: Sick Days and Adrenal Crisis

Missing a dose temporarily leaves your body without its necessary cortisol replacement. If you are sick, injured, or under severe physical stress, missing a dose or failing to take your increased “stress dose” is extremely dangerous ^[6][3]. Without adequate hydrocortisone during these stressful periods, you are at a high risk of an adrenal crisis ^[7][1].

An adrenal crisis is a life-threatening emergency. Symptoms can include severe fatigue, unusual weakness, fainting or dizziness (low blood pressure), nausea, confusion, and hypoglycemia (dangerously low blood sugar, which is particularly common in children) ^[3][8]. This list is not exhaustive.

Emergency Instructions: If you suspect an adrenal crisis, experience severe weakness, fainting, or persistent vomiting, do not wait.

• Administer emergency intramuscular (injectable) hydrocortisone exactly as you were trained to do ^[5].
• Call local emergency services (e.g., 911) or go to the nearest emergency department right away ^[5].
• If you do not have an emergency kit or are not trained to use it, call emergency services immediately and inform them that you have adrenal insufficiency and require emergency parenteral (IV/IM) hydrocortisone.

The Long-Term Effects of Chronically Missed Doses

Consistently taking your medication is just as important as emergency management. When hydrocortisone doses are chronically missed or skipped over time, the lower levels of cortisol provide less feedback to your brain. This causes the pituitary gland to release more of a signaling hormone called ACTH ^[1]. Because patients with Classic CAH have a severe deficiency of the 21-hydroxylase enzyme, their overstimulated adrenal glands cannot make enough cortisol. Instead, the glands accumulate precursor hormones and produce excess androgens ^[2].

Androgens are hormones that contribute to male-typical traits, though everyone has them. Persistent androgen excess causes virilization, which is the development of exaggerated physical characteristics. Depending on the individual, ongoing androgen excess can lead to excess body hair (hirsutism), deepening of the voice, hair loss, and irregular menstrual cycles or reduced fertility ^[9][10].

In growing children, excess androgens accelerate bone aging. This can cause the growth plates to close prematurely, resulting in a shorter final adult height ^[7][11].

Furthermore, chronic undertreatment leaves your body in a constant state of vulnerability, which can increase the likelihood of slipping into an adrenal crisis during unexpected physical stress ^[12].