Prednisone causes a wide range of side effects, from mild nuisances like insomnia and increased appetite to serious complications like bone loss and high blood sugar. The likelihood and severity depend heavily on two factors: how much you’re taking and how long you take it. A short course of a few days carries far less risk than weeks or months of daily use, but even brief courses can cause noticeable changes in mood, sleep, and energy.
Early Side Effects You’ll Notice First
The side effects that show up within the first few days are often the most jarring because they feel so different from your normal baseline. Difficulty falling or staying asleep is extremely common, even at moderate doses. Many people also notice a sharp increase in appetite and a jittery, wired feeling that’s hard to describe. Some people feel unusually upbeat or energized, while others become irritable or anxious. These mood shifts can be dramatic enough that the people around you notice before you do.
Other early effects include fluid retention (puffy face, swollen ankles), headaches, and increased sweating. Stomach discomfort is common, especially if you take prednisone on an empty stomach. Taking it with food in the morning helps with both the stomach irritation and the insomnia, since the drug’s stimulating effects have more time to wear off before bedtime.
Mood and Mental Health Effects
Prednisone’s impact on mood goes beyond everyday irritability. Two large analyses found that about 28% of patients experience mild to moderate psychiatric effects, while nearly 6% develop severe reactions. In one study of patients on long-term low-dose therapy, 60% experienced a mood or anxiety disorder at some point during treatment. Children appear especially vulnerable: up to half of kids taking oral steroids show increased anxiety, irritability, or behavioral changes.
The range of possible reactions is broad. Some people feel euphoric and restless. Others become tearful, anxious, or quick to anger. In rare cases, prednisone can trigger confusion, paranoia, or psychosis. These severe reactions are uncommon but more likely at higher doses. If you or someone close to you notices a significant personality shift while on prednisone, that’s worth reporting to your prescriber promptly.
Blood Sugar and Metabolic Changes
Prednisone raises blood sugar by making your cells more resistant to insulin and prompting your liver to release more glucose. This isn’t a subtle effect. Among people with no prior history of diabetes who take steroids for a month or longer, about 32% develop elevated blood sugar. Roughly 19% go on to meet the threshold for a diabetes diagnosis.
If you already have diabetes, expect your numbers to run higher than usual, particularly in the afternoon and evening. Even if you’ve never had blood sugar issues, a longer course of prednisone may warrant monitoring. The effect is generally reversible once you stop the medication, but it can unmask a tendency toward diabetes that sticks around afterward.
Weight Gain
Weight gain on prednisone comes from multiple directions at once. The drug increases appetite, promotes fat storage (especially around the face, neck, and abdomen), and causes fluid retention. The higher the dose and the longer you take it, the more pronounced the changes become. The characteristic “moon face” and redistribution of body fat are cosmetically distressing for many people and can take weeks to months to resolve after stopping.
Limiting sodium helps reduce fluid retention, and being aware of the appetite increase can help you make deliberate food choices rather than eating on autopilot. That said, some degree of weight change is difficult to avoid on longer courses.
Bone Loss
This is one of the most significant long-term risks, and it starts earlier than most people realize. Even at doses as low as 2.5 mg daily, prednisone has been shown to cause more than an 8% decrease in bone mineral density after just 20 weeks. That’s a meaningful loss in under five months, and it makes fractures, particularly of the spine and hip, a real concern for anyone on extended therapy.
If you’ll be taking prednisone for more than a few weeks, your doctor will likely recommend calcium (1,000 to 1,200 mg daily, ideally from food) and vitamin D (600 to 800 IU daily). Depending on your age and other risk factors, a bone density scan and additional bone-protecting treatment may be appropriate.
Eye Problems
Long-term steroid use raises the risk of two specific eye conditions. The first is increased pressure inside the eye, which can lead to glaucoma. The second is a type of cataract that forms on the back surface of the lens. Both risks increase with higher doses and longer treatment. If you’re on prednisone for an extended period, periodic eye exams can catch pressure changes or lens clouding before they cause noticeable vision loss.
Immune Suppression and Infection Risk
Prednisone works by dialing down your immune system, which is exactly why it’s prescribed for inflammatory and autoimmune conditions. The trade-off is that your body becomes less capable of fighting off infections. Ordinary colds can linger, minor wounds may heal slowly, and infections that your immune system would normally handle easily can become serious.
Warning signs to watch for include a fever or chills, a sore throat that won’t quit, painful urination, mouth sores, or wounds that refuse to heal. These can signal an infection that needs prompt treatment. The risk is proportional to dose and duration: a five-day burst carries minimal immune risk, while months of moderate-to-high doses significantly blunts your defenses.
Stomach and Digestive Issues
Prednisone on its own causes peptic ulcers in only about 0.4% to 1.8% of patients, which is lower than many people assume. The real danger comes from combining prednisone with anti-inflammatory painkillers like ibuprofen or naproxen. That combination substantially raises ulcer risk, and people taking both are typically prescribed a stomach-protecting acid reducer.
Even without ulcers, general stomach discomfort, bloating, and nausea are common. People over 65, heavy smokers, heavy drinkers, and anyone with a history of stomach ulcers face higher gastrointestinal risk and may benefit from protective medication even without adding painkillers to the mix.
Why You Can’t Stop Suddenly
When you take prednisone for more than a week or two, your adrenal glands (which normally produce your body’s own version of this hormone) slow down production because the drug is doing their job. If you stop abruptly, your body can’t pick up the slack fast enough. The result is withdrawal symptoms that include severe fatigue, body aches, joint pain, nausea, lightheadedness, and irritability.
This is why prednisone is tapered gradually rather than stopped cold. Tapering gives your adrenal glands time to wake back up and resume normal hormone production. The speed of the taper depends on how long you’ve been on the medication and at what dose. Even with a careful taper, some people feel off for a few weeks as their body readjusts. If withdrawal symptoms become severe during a taper, your prescriber can slow the schedule down.
Dose and Duration Matter Most
Nearly every side effect of prednisone follows the same pattern: higher doses and longer courses mean greater risk. A three-day burst for a poison ivy rash is a fundamentally different experience from six months of daily therapy for lupus. Short courses may cause temporary insomnia, mood shifts, and appetite changes that resolve within days of stopping. Long courses can lead to the full spectrum of effects described above, including bone loss, blood sugar disruption, weight redistribution, and weakened immunity.
Your individual risk also depends on age, existing health conditions, and what other medications you’re taking. People with diabetes, osteoporosis, a history of mental health conditions, or stomach problems face amplified risks in those specific areas. Understanding which side effects are most relevant to your situation helps you and your doctor monitor the right things and intervene early when needed.