Prednisone causes a wide range of side effects that depend heavily on dose and duration. Short courses of a few days may only produce insomnia, mood changes, and increased appetite. Longer use, especially at higher doses, can affect bones, blood sugar, immune function, eye health, and body composition. Understanding which effects are likely, and when they become a concern, helps you know what to watch for.
Sleep, Mood, and Mental Health Effects
Insomnia is one of the most common complaints. In one study, 72% of patients experienced trouble sleeping after starting corticosteroid therapy. Taking your dose in the morning rather than at night can help, since the drug’s stimulating effect peaks in the hours after you swallow it.
Mood and behavioral changes are nearly as common. Roughly half of all corticosteroid users experience some type of behavioral shift, and about one in four develops noticeable mood disturbances. These range from mild irritability or an unusual sense of euphoria to more serious problems like depression, anxiety, or, rarely, psychosis. Depression symptoms appear in about 22% of users, anxiety in about 8%, and manic symptoms in roughly 11%. A small percentage (around 4 to 5%) develop steroid-induced psychosis, which can include confusion, hallucinations, or paranoid thinking. These psychiatric effects tend to improve once the dose is lowered or stopped, but they’re worth flagging to your prescriber early.
Blood Sugar and Metabolic Changes
Prednisone makes your cells resist insulin, reducing their ability to absorb sugar from the bloodstream by 30 to 50%. The result is higher blood sugar, sometimes dramatically so. In hospital settings where patients receive higher doses, 86% experience at least one episode of elevated blood sugar, and nearly half maintain averages above 140 mg/dL. Outside the hospital, glucose levels can rise up to 68% above baseline.
This matters even if you’ve never had diabetes. Up to 46% of people without a prior diabetes diagnosis develop high blood sugar during corticosteroid treatment. If you already have diabetes, expect your levels to be harder to control and your medication needs to increase temporarily. Blood sugar typically returns to normal after prednisone is stopped, but prolonged courses can sometimes trigger lasting metabolic changes.
Weight Gain and Body Shape Changes
About 40% of people on long-term corticosteroids gain more than 2 kilograms (roughly 4.5 pounds) beyond their usual weight, and about 10% gain 10% or more of their body weight. Younger women tend to be most affected, gaining an average of 3.6 kg during treatment compared to 2 kg in similar women not taking the drug.
Prednisone also redistributes fat in distinctive ways. Fat tends to accumulate in the face (sometimes called “moon face”), the upper back between the shoulders, and the abdomen, while the arms and legs may stay relatively thin. These cushingoid features are among the most visible and distressing side effects for many people, and they generally improve gradually after the drug is discontinued, though it can take weeks to months.
Bone Loss and Fracture Risk
Corticosteroids are the most common drug-related cause of osteoporosis. Bone density loss begins quickly, with studies documenting losses of about 2% per year at the lumbar spine in patients on chronic low-dose therapy who aren’t taking preventive supplements. Calcium (1,000 mg daily) and vitamin D (500 units daily) can cut that loss significantly, reducing it to under 1% per year. Your doctor will often recommend these supplements from the start of a longer course and may check your bone density if treatment extends beyond a few months.
Immune Suppression and Infection Risk
Prednisone works partly by dampening the immune system, which is useful for autoimmune conditions but leaves you more vulnerable to infections. The risk scales with dose. At 7.5 mg per day or more, your risk of shingles roughly doubles. At doses above 15 mg per day, the odds of developing tuberculosis increase nearly eightfold compared to non-users. High doses (30 mg or more) dramatically raise the risk of a serious fungal lung infection called pneumocystis pneumonia.
Even at moderate doses, everyday infections like colds and urinary tract infections can hit harder and last longer. Wounds may heal more slowly. If you develop a fever, persistent cough, or signs of infection while on prednisone, it’s worth getting checked sooner rather than later since your body’s usual early-warning inflammatory response may be muted.
Eye Problems
Long-term corticosteroid use increases the risk of both cataracts and glaucoma. In one large study of patients on chronic inhaled corticosteroids, about 16% developed cataracts and nearly 4% developed glaucoma, with the highest rates (close to 40% for cataracts) seen at the highest doses. Oral prednisone delivers a larger systemic dose than inhalers, so the risk is at least comparable. If you’re on prednisone for more than a few months, periodic eye exams can catch rising eye pressure or early lens changes before they progress.
How Dose and Duration Shape Risk
Not all prednisone courses carry the same risk profile. A five-day burst for a severe asthma flare is a different situation from months of daily therapy for lupus. Research on long-term use at doses under 5 mg per day suggests that very low doses are reasonably well tolerated for years, with the most common problems being skin thinning and easy bruising. Serious complications like diabetes, cataracts, and high blood pressure remain relatively uncommon at that level, though they aren’t zero.
Above 5 mg per day, risks begin climbing more steeply. The jump from 5 to 10 mg roughly doubles the likelihood of several side effects, and doses above 20 to 30 mg per day are where the most serious complications cluster. Duration matters just as much as dose: three weeks is a commonly cited threshold after which the adrenal glands may start suppressing their own cortisol production, which creates problems if you stop the drug abruptly.
Stopping Prednisone Safely
Your adrenal glands normally produce cortisol on their own. When you take prednisone, especially at doses above about 5 mg daily for more than three to four weeks, your adrenals scale back production because the drug is doing their job. Stop suddenly and your body can’t compensate, leading to adrenal insufficiency: fatigue, muscle weakness, nausea, dizziness, and in severe cases, a dangerous drop in blood pressure.
If you’ve been on prednisone for less than three to four weeks, you can generally stop without tapering regardless of dose. For longer courses, a gradual reduction is essential. Tapering typically involves stepping the dose down over weeks until you reach a physiologic range (around 4 to 6 mg of prednisone daily), then either continuing to taper slowly or testing your cortisol levels to confirm your adrenals have woken back up.
During a taper, some people experience withdrawal symptoms like joint pain, fatigue, and mood dips even when adrenal function is recovering normally. This glucocorticoid withdrawal syndrome isn’t dangerous, but it can be uncomfortable enough that a slower taper becomes necessary. If symptoms flare, your prescriber may briefly bump the dose back up before resuming a more gradual reduction.
Effects on Children’s Growth
In children, long-term prednisone can slow linear growth. One controlled study of children treated for kidney disease found that height was largely unaffected through the first three years of therapy, but by five years, children had lost about 0.4 standard deviations in height compared to where they started. Among those on long-term treatment beyond five years, 22% met the criteria for short stature, compared to 6% in a control group. The effect is dose-dependent: higher cumulative doses correlate with greater height suppression. Children who also develop obesity from prednisone tend to be shorter than other obese children of the same age, suggesting the drug’s growth effects go beyond simple weight-related changes.