Fludrocortisone is a prescription medication used to replace a hormone your adrenal glands aren’t making enough of. It’s approved for two conditions: primary and secondary adrenal insufficiency (including Addison’s disease) and salt-losing congenital adrenal hyperplasia. Doctors also prescribe it off-label to treat orthostatic hypotension, a condition where blood pressure drops when you stand up.
How Fludrocortisone Works
Your adrenal glands normally produce a hormone called aldosterone, which tells your kidneys to hold onto sodium and water. This keeps your blood volume and blood pressure stable. When your adrenal glands can’t make enough aldosterone, your body loses too much salt through urine, blood pressure drops, and you can become dangerously dehydrated.
Fludrocortisone is a synthetic version of aldosterone, but roughly 10 times more potent. It signals your kidneys to reabsorb sodium and water, which increases blood volume and raises blood pressure. It also makes blood vessels more sensitive to the natural signals that cause them to constrict, providing a second mechanism for keeping blood pressure up.
Addison’s Disease and Adrenal Insufficiency
This is the primary reason fludrocortisone exists. In Addison’s disease, the adrenal glands are damaged (often by the immune system) and can’t produce enough cortisol or aldosterone. Without aldosterone replacement, people with Addison’s disease lose salt rapidly, develop low blood pressure, and can go into adrenal crisis, a life-threatening emergency.
Fludrocortisone handles the aldosterone side of the equation. It’s almost always paired with another medication, typically hydrocortisone (10 to 30 mg daily) or a similar glucocorticoid, which replaces the missing cortisol. Together, these two drugs cover both hormones the adrenal glands would normally produce.
The typical dose ranges from 0.1 mg taken three times a week up to 0.2 mg once daily, depending on how much replacement you need. Most people take 0.1 mg once a day. Dosing isn’t always static. Some people need higher doses in the summer or in warmer climates because they lose more sodium through sweat. Your doctor may adjust the dose seasonally or if you move to a different climate.
Salt-Losing Congenital Adrenal Hyperplasia
This is a genetic condition present from birth where the adrenal glands can’t produce aldosterone properly. Infants and children with the salt-losing form lose dangerous amounts of sodium, which can cause dehydration, poor weight gain, and potentially fatal salt-wasting crises in the first weeks of life. Fludrocortisone replaces the missing hormone, typically at doses of 0.1 to 0.2 mg daily. Many people with this condition take fludrocortisone for life.
Orthostatic Hypotension and POTS
Fludrocortisone is widely used off-label for orthostatic hypotension, a condition where blood pressure falls significantly when you stand up, causing dizziness, lightheadedness, or fainting. Expert consensus from the American Academy of Family Physicians supports this use, though the clinical evidence is limited. One study of just 17 patients over three weeks showed improvement in symptom scores.
It’s also sometimes prescribed for postural orthostatic tachycardia syndrome (POTS), a related but distinct condition where standing causes a rapid heart rate and symptoms of dizziness without the characteristic blood pressure drop. In both cases, the logic is the same: fludrocortisone increases blood volume, which helps your cardiovascular system cope with the shift to standing.
The starting dose for orthostatic hypotension is usually 0.1 mg once daily, sometimes increased to 0.2 mg. Higher doses don’t improve symptoms but do increase the risk of side effects. This is an important distinction from the adrenal insufficiency use: in orthostatic hypotension, fludrocortisone is treating a symptom rather than replacing a missing hormone, so the risk-benefit calculation is different, and long-term use carries more concern.
Common Side Effects
Because fludrocortisone causes your body to retain sodium and water, the most predictable side effects are related to fluid overload. A weight gain of 2 to 5 pounds is expected and considered normal. Some ankle swelling is also typical and not necessarily a reason to stop the medication.
The most common side effects include:
- High blood pressure when lying down (supine hypertension): This is the most frequent dose-limiting problem. If blood pressure rises too high, the dose is usually reduced to 0.05 mg daily.
- Low potassium: Fludrocortisone causes the kidneys to excrete potassium while holding onto sodium. This is common enough that many people take a potassium supplement alongside it or are advised to eat potassium-rich foods like bananas, potatoes, and leafy greens.
- Ankle and leg swelling: Mild peripheral edema from fluid retention.
Long-term risks are more serious, particularly for people taking fludrocortisone for orthostatic hypotension rather than adrenal insufficiency. Prolonged use can lead to thickening of the heart’s left ventricle, kidney damage, and a higher rate of hospitalization. Your doctor will typically monitor your weight, blood pressure, and potassium levels regularly to catch problems early.
Drug Interactions to Know About
Fludrocortisone’s tendency to lower potassium creates a ripple effect with several other medications. Low potassium increases the risk of dangerous heart rhythm problems, so combining fludrocortisone with drugs that also lower potassium or affect heart rhythm requires caution. Digoxin, a common heart medication, is a notable example: low potassium from fludrocortisone can amplify digoxin’s toxicity.
Anti-inflammatory painkillers like diclofenac and other NSAIDs increase the risk of gastrointestinal bleeding when taken with fludrocortisone. If you use over-the-counter painkillers regularly, this is worth discussing with your prescriber. Blood thinners may also be affected, as fludrocortisone can enhance their effects, potentially requiring closer monitoring.
Practical Tips While Taking Fludrocortisone
People on fludrocortisone are often advised to eat a liberal amount of salt, which is the opposite of the usual dietary advice. This works with the medication to maintain blood volume and prevent dehydration. At the same time, you need to ensure adequate potassium intake to offset the potassium your kidneys are now excreting at a higher rate.
Timing is straightforward: most people take it once in the morning. Some require twice-daily or every-other-day dosing depending on their response. If you’re taking it for adrenal insufficiency, it’s a lifelong medication, and you should never stop it abruptly. Missing doses or running out can lead to a rapid drop in blood pressure and a potential adrenal crisis. Keeping extra supply on hand and wearing medical alert identification are standard precautions for people with adrenal insufficiency.