Prednisone Side Effects: What to Expect & When to Call Your Doctor

Prednisone is a synthetic corticosteroid — a man-made version of cortisol, the hormone your adrenal glands naturally produce. It is a powerful anti-inflammatory and immunosuppressant used for an enormous range of conditions: asthma flares, allergic reactions, autoimmune diseases (lupus, rheumatoid arthritis, inflammatory bowel disease), organ transplant rejection prevention, and certain cancers. It is sold under the brand name Deltasone and widely available as a generic. Understanding prednisone's side effect profile requires distinguishing between what happens with short-term use (days to a few weeks) versus prolonged use (months to years).

Short-Term Side Effects

Even a brief course of prednisone can produce significant effects on mood, sleep, blood sugar, and fluid balance.

Serious Side Effects: When to Seek Help Immediately

Long-Term Risks: What Months of Prednisone Can Do

Adrenal suppression — the reason you cannot stop abruptly: The hypothalamic-pituitary-adrenal (HPA) axis normally regulates cortisol production. When exogenous corticosteroids are taken consistently, the body's feedback system recognizes high steroid levels and downregulates the adrenal glands' own production. With prolonged use, the adrenal glands can atrophy — shrink and lose their capacity to produce cortisol independently. Abruptly stopping prednisone after this has occurred causes adrenal insufficiency (sometimes called adrenal crisis) — a life-threatening shortage of the cortisol the body needs to function. Always taper prednisone slowly under medical supervision when ending a prolonged course. How slowly depends on how long you've been taking it and the exposure level involved — your prescriber will determine the appropriate schedule.

Osteoporosis and fracture risk: Corticosteroids directly inhibit bone formation and increase bone resorption. Even a few months of prednisone can cause significant bone density loss, and the risk of fractures — particularly vertebral (spine) fractures — increases substantially with longer-term use. Patients on chronic corticosteroid therapy are typically advised to take calcium and vitamin D supplements, and may be prescribed bisphosphonate medications (like alendronate) to protect bone density. Bone density testing (DEXA scan) is often recommended for patients on prolonged courses.

Immunosuppression: Prednisone suppresses multiple arms of the immune system. This is the mechanism that makes it therapeutically useful for autoimmune and inflammatory conditions — but it also means a reduced ability to fight infections. Patients on prednisone are more susceptible to bacterial, viral, and fungal infections, and the normal warning signs of infection (fever, inflammation) may be blunted or absent. Live vaccines should generally not be given to patients on significant immunosuppressive doses of prednisone. Report any signs of infection to your prescriber promptly.

Cushing's Syndrome: What Long-Term Steroids Can Look Like

Prolonged exposure to high levels of corticosteroids — whether from the adrenal glands' own overproduction or from medications like prednisone — causes a recognizable syndrome named for Harvey Cushing. Symptoms of corticosteroid-induced Cushing's syndrome include: central weight gain with a round "moon face," a fat pad between the shoulder blades ("buffalo hump"), easy bruising, stretch marks (striae), thinning skin, slow wound healing, muscle weakness (particularly in the thighs), and high blood pressure. These changes reverse gradually after prednisone is tapered and stopped, but full recovery can take months.

Blood Sugar and Diabetes Risk

Prednisone raises blood glucose through multiple mechanisms — it reduces insulin sensitivity, increases glucose production by the liver, and promotes glycogen breakdown. In patients without diabetes, brief courses typically cause minor, transient blood sugar elevations. In patients with diabetes, even short courses can cause significant glucose spikes requiring insulin or medication adjustments. With prolonged use, previously non-diabetic patients can develop steroid-induced diabetes. Patients with diabetes or pre-diabetes should monitor blood glucose more closely during prednisone courses and discuss management with their provider.

Cataracts and Eye Effects

Long-term corticosteroid use is associated with the development of posterior subcapsular cataracts — a specific type of lens opacity that can impair vision. Glaucoma (elevated intraocular pressure) is also a recognized risk. Patients on chronic corticosteroid therapy should have periodic eye examinations to monitor for these complications.

Frequently Asked Questions

Why does prednisone cause insomnia and mood changes?

Corticosteroids like prednisone affect the central nervous system, altering the normal diurnal cortisol rhythm that helps regulate the sleep-wake cycle. Prednisone is stimulating, and taking it in the morning (rather than at night) minimizes sleep disruption. Mood effects — euphoria, irritability, anxiety, and in some cases significant depression or even psychosis at higher exposures — are caused by corticosteroid effects on brain regions involved in mood regulation, including the limbic system. These effects typically reverse when the medication is stopped or reduced.

Why can't I stop prednisone abruptly?

The adrenal glands normally produce cortisol, a hormone essential for life. When you take prednisone, the brain's feedback system detects high corticosteroid levels and signals the adrenal glands to reduce their own cortisol production. With prolonged use, the adrenal glands can atrophy. If prednisone is stopped abruptly, the body can't produce enough cortisol on its own — a dangerous condition called adrenal insufficiency or adrenal crisis — which can cause severe weakness, low blood pressure, nausea, and collapse. A gradual taper allows the adrenal glands time to resume normal function.

Does prednisone cause permanent weight gain?

Weight gain on prednisone has two components: fluid retention (which resolves relatively quickly when the medication is stopped) and true fat redistribution (which can be more persistent with longer-term use). The characteristic pattern of steroid-related weight gain — increased abdominal fat, "moon face," and "buffalo hump" — is part of Cushing's syndrome and typically improves after stopping, though it may take several months to fully reverse. Limiting sodium intake can help control fluid retention while on the medication.