Prednisone reliably raises blood sugar in most people who take it, though the size of the increase varies enormously depending on dose, duration, and whether you already have diabetes. In one study, a short course of prednisone roughly doubled a standard measure of insulin resistance in otherwise healthy people. For someone with well-controlled type 2 diabetes, the spike can be considerably larger and harder to manage. The timing, the dose threshold, and your personal risk factors all shape how big the effect is and how long it lasts.
Why Prednisone Raises Blood Sugar
Prednisone is a glucocorticoid, a class of steroids your body actually produces naturally through cortisol. When you take a pharmaceutical dose, the drug pushes your metabolism in ways that make glucose harder to control from multiple directions at once. Your liver ramps up glucose production, your muscles become less efficient at pulling sugar out of the bloodstream, and your fat tissue starts behaving differently. A study in healthy volunteers found that prednisolone treatment triggered significant hyperinsulinemia and hyperglucagonemia while more than doubling a common index of insulin resistance.
The effect is not limited to how your body responds to insulin. Prednisone also appears to damage the cells that produce insulin in the first place. Research on human pancreatic islets exposed to glucocorticoids showed that insulin-secreting beta cells produced less insulin and died at higher rates, with reduced levels of key proteins those cells need to function properly.1PubMed Central. Glucocorticoid induces human beta cell dysfunction by involving riborepressor GAS5 LincRNA So the drug simultaneously makes your body more resistant to insulin and undermines your ability to produce enough of it. That two-pronged assault is why the blood sugar effect can be so pronounced.
How Much the Increase Looks Like in Numbers
Giving a single number for “how much” prednisone raises blood sugar is genuinely difficult because the range is so wide. But the research gives us useful reference points.
In healthy volunteers given prednisolone, a measure called the HOMA index, which estimates insulin resistance from fasting glucose and insulin levels, jumped from about 7 to about 17 on average. That is roughly a 2.4-fold increase in insulin resistance from the drug alone.2PubMed. Preferential stimulation of abdominal subcutaneous lipolysis after prednisolone exposure in humans These were people without diabetes, so their bodies still had the capacity to compensate by producing more insulin. Even so, fasting insulin rose substantially and glucagon (a hormone that raises blood sugar) increased as well.
In people with type 2 diabetes, the picture is worse. A study comparing the effects of short-term prednisone in people with and without type 2 diabetes found that the glucose area under the curve, essentially the total blood sugar exposure over time, rose significantly more in the diabetes group. Beta cell function, measured by a standard index, dropped, and the early insulin response to glucose fell by roughly 69% in the diabetes group compared to about 34% in those without diabetes.3PLoS ONE. Effect of short-term prednisone on beta-cell function in subjects with type 2 diabetes mellitus and healthy subjects That difference in early insulin response is clinically meaningful because it is your body’s first defense against a post-meal glucose spike.
When the Spike Hits During the Day
One of the more useful things to know about prednisone-induced blood sugar rises is that they follow a predictable daily pattern. If you take oral prednisone in the morning, which is the standard dosing schedule, your blood sugar does not spike immediately. Instead, glucose levels tend to climb through the afternoon and peak in the late afternoon through late evening. Continuous glucose monitoring in children receiving high-dose glucocorticoid treatment confirmed that the highest sensor glucose values during a 24-hour period appeared between roughly 4:00 PM and 11:00 PM for those on oral prednisolone.4PubMed. Continuous Glucose Monitoring Profiles in Children Receiving High-Dose Glucocorticoid Treatment
This timing pattern matters for several practical reasons. If your doctor measures only a fasting morning glucose to monitor you while on prednisone, that reading could look entirely normal while your afternoon and evening sugars are dangerously high. Similarly, if you are checking your own blood sugar at home, a single morning finger stick gives an incomplete and potentially misleading picture. The late-day peak also explains why many people on prednisone feel fine in the morning but experience increased thirst, frequent urination, or fatigue as the day wears on.
Dose and the Steep Risk Curve
The relationship between prednisone dose and blood sugar is not a gentle slope; it is more of a cliff. A retrospective study of nearly 300 dermatology patients receiving glucocorticoids found that the risk of developing steroid-induced diabetes rose steeply once the daily dose exceeded about 1.0 mg per kilogram of body weight. At 1.2 mg/kg/day, the odds ratio jumped to nearly 4, meaning those patients were roughly four times as likely to develop steroid-induced diabetes as those on lower doses.5PubMed Central. Associated Factors and Dose–Response of Steroid-Induced Diabetes Mellitus in Dermatology Inpatients – A Retrospective Study When the average daily dose itself was modeled as a risk factor, the odds ratio was an eye-catching 29, reflecting just how powerful high-dose glucocorticoid therapy is at disrupting glucose metabolism.
For context, a typical short prednisone “burst” for something like a flare of asthma or poison ivy might be 40 to 60 mg per day for 5 to 7 days. For someone weighing about 70 kg (roughly 155 pounds), that translates to about 0.6 to 0.85 mg/kg/day, which is below the steepest part of the dose-response curve. That does not mean blood sugar is unaffected at lower doses. Even low-dose prednisolone, studied in patients with rheumatic diseases, acutely increased the liver’s glucose production, reduced insulin’s ability to suppress that production, and cut both the first and second phases of insulin secretion.6PubMed Central. Effects of low-dose prednisolone on hepatic and peripheral insulin sensitivity, insulin secretion, and abdominal adiposity in patients with inflammatory rheumatologic disease The effect was smaller than you would see at higher doses, but it was measurable and statistically clear.
Who Gets Hit the Hardest
Not everyone reacts to prednisone the same way, and certain risk factors make a much bigger blood sugar response more likely. In the dermatology study described above, the strongest independent predictor of developing steroid-induced diabetes was having a family history of diabetes, which carried an odds ratio above 11.5PubMed Central. Associated Factors and Dose–Response of Steroid-Induced Diabetes Mellitus in Dermatology Inpatients – A Retrospective Study That is a much higher risk multiplier than most people would expect from family history alone, and it suggests that the genetic vulnerability to insulin resistance is already simmering in these individuals before the steroid ever enters the picture.
Other factors that raised risk in the same study included higher BMI, existing hypertension, elevated uric acid levels, and concurrent use of immunosuppressant medications. Being older compounds the problem as well, because aging naturally reduces insulin sensitivity and beta cell reserve. People who already have prediabetes or metabolic syndrome are sitting closer to the edge, and prednisone can push them over it. The study found that about 14% of the patients developed full-blown steroid-induced diabetes, with another 6% showing impaired glucose regulation.5PubMed Central. Associated Factors and Dose–Response of Steroid-Induced Diabetes Mellitus in Dermatology Inpatients – A Retrospective Study
For people who already have diagnosed type 2 diabetes, the issue is not whether blood sugar will rise but by how much and how to stay ahead of it. As mentioned earlier, their beta cell function drops proportionally more than in healthy individuals, and their glucose excursions are larger. If your diabetes is already poorly controlled, the effect can be amplified further. A study of patients with diabetes receiving steroid injections for musculoskeletal pain found that those with a pre-injection HbA1c above 7% experienced significantly larger blood sugar increases the day after the injection compared to those with better baseline control.7PubMed Central. Changes in Blood Glucose Level After Steroid Injection for Musculoskeletal Pain in Patients With Diabetes
Steroid Injections Are Not a Free Pass
A common assumption is that a steroid injection into a joint or around a tendon is a “local” treatment that would not affect blood sugar the way oral prednisone does. The research says otherwise. In the same injection study, blood glucose rose significantly the day after the injection in patients with diabetes. Interestingly, neither the specific injection site nor the injected steroid dose predicted the size of the blood sugar increase. What did predict it was the patient’s baseline glucose control, measured by HbA1c.7PubMed Central. Changes in Blood Glucose Level After Steroid Injection for Musculoskeletal Pain in Patients With Diabetes
The good news is that the effect from a single injection tends to be brief. Blood glucose was significantly elevated one day after injection but not two days later. So the disruption is real but transient, at least for a one-time injection. If you have diabetes and your doctor recommends a corticosteroid injection, the smart move is to plan for closer blood sugar monitoring for a day or two afterward rather than avoiding the injection entirely.
Short Courses Versus Long-Term Therapy
The clinical picture changes considerably depending on whether you are taking a five-day prednisone taper or staying on the drug for weeks or months. Short courses cause temporary insulin resistance and blood sugar spikes that typically resolve once the drug clears your system. For most people without diabetes, a few days of higher blood sugar from a brief prednisone burst is uncomfortable but not dangerous.
Long-term exposure is a different animal. Research on patients with inflammatory rheumatic disease found that people who had been taking prednisolone for extended periods showed reduced ability to suppress liver glucose production and impaired nonoxidative glucose disposal compared to patients not on glucocorticoids, even at low maintenance doses.6PubMed Central. Effects of low-dose prednisolone on hepatic and peripheral insulin sensitivity, insulin secretion, and abdominal adiposity in patients with inflammatory rheumatologic disease When glucocorticoid exposure becomes chronic, the metabolic disruption can progress from reversible insulin resistance to actual cardiometabolic disease.8PubMed Central. Molecular Mechanisms of Glucocorticoid-Induced Insulin Resistance That progression from “temporarily elevated blood sugar” to “new diabetes that may or may not resolve after the drug stops” is one of the most important distinctions in this whole topic.
Prednisone and Pregnancy
Corticosteroids are sometimes given to pregnant women at risk of preterm delivery to accelerate fetal lung maturation. This is a well-established and often life-saving intervention, but it causes maternal blood sugar to rise, and that effect is especially concerning in women who already have gestational diabetes.
In one study of pregnant women receiving antenatal corticosteroids, roughly 72% developed some degree of abnormal blood sugar, either impaired glucose or frank diabetes. However, the effect was transient in most patients, with blood sugar normalizing within about five days after the last dose.9Journal of Postgraduate Medical Institute. Effect of Antenatal Corticosteroids on Maternal Blood Glucose Levels A randomized trial comparing two commonly used steroids for this purpose, dexamethasone and betamethasone, found that dexamethasone produced somewhat lower median blood glucose levels and fewer hyperglycemic episodes in women with mild gestational diabetes, particularly on the second and third days of treatment.10PubMed. Antenatal dexamethasone vs betamethasone on glycemic control in mild gestational diabetes – a randomized clinical trial
The concern in pregnancy goes beyond maternal comfort. Steroid-induced maternal hyperglycemia can lead to fetal hyperinsulinemia, and administering corticosteroids close to delivery carries a risk of neonatal hypoglycemia after birth, especially in women with gestational diabetes.11PubMed Central. Gestational Diabetes Mellitus and Antenatal Corticosteroid Therapy—A Narrative Review of Fetal and Neonatal Outcomes This does not mean antenatal steroids should be withheld. It means the blood sugar response needs to be monitored aggressively and managed tightly when they are given to women with diabetes.
Children on High-Dose Steroids
Pediatric patients, especially those undergoing chemotherapy for conditions like acute lymphocytic leukemia, often receive prolonged high-dose steroids as part of their treatment protocol. A study of 91 pediatric leukemia patients found that about 12% developed hyperglycemia during steroid therapy, with another 13% showing transient or borderline elevations. The onset was not immediate, typically appearing between days 2 and 16 of treatment, with clustering around days 4 and 10.12PubMed Central. The Incidence of Steroid-Induced Hyperglycemia in Pediatric Patients With Acute Lymphocytic Leukemia
The delayed and variable onset is important for parents and clinicians to understand. Checking blood sugar only during the first couple of days of steroid therapy might miss the problem entirely. Children in these protocols are typically monitored closely, but the data confirms that blood sugar surveillance needs to extend through the full course of treatment, not just the initial days.
Practical Steps If You Are Starting Prednisone
If your doctor prescribes prednisone, a few practical measures can help you catch blood sugar problems early and manage them effectively. For a short course of five to seven days, most people without diabetes do not need to do anything special, but it is worth knowing the symptoms of high blood sugar: increased thirst, frequent urination, blurred vision, and unusual fatigue, particularly in the afternoon and evening when the glucose effect peaks.
If you already have diabetes, talk with your provider about adjusting your medications before you start. Because prednisone’s glucose effect is concentrated in the afternoon and evening hours, your usual morning diabetes medication may not cover the problem adequately. Some clinicians add or adjust intermediate-acting insulin to coincide with the expected glucose rise. Checking blood sugar more often, including before dinner and at bedtime, gives a far more accurate picture than relying only on a fasting morning check.
For anyone on prednisone longer than a couple of weeks, periodic blood sugar screening is reasonable even if you have never had diabetes, especially if you carry other risk factors like family history, higher body weight, or older age. The roughly 14% incidence of steroid-induced diabetes found in one inpatient study is not trivial, and catching it early allows for management before blood sugar levels cause additional organ stress.
Does Blood Sugar Go Back to Normal After Stopping?
For most people on short courses, yes. Blood sugar typically returns to baseline within days of stopping prednisone, and the study of steroid injections found normalization by the second day after a single injection.7PubMed Central. Changes in Blood Glucose Level After Steroid Injection for Musculoskeletal Pain in Patients With Diabetes In pregnant women receiving antenatal corticosteroids, blood sugar largely normalized within five days.9Journal of Postgraduate Medical Institute. Effect of Antenatal Corticosteroids on Maternal Blood Glucose Levels
The picture is less clear for people who have been on prednisone for months. While stopping the drug removes the ongoing pharmacological assault on insulin sensitivity, some of the metabolic changes, particularly alterations in body fat distribution and residual insulin resistance, can take longer to resolve. In some patients with predisposing risk factors, the steroid-induced diabetes becomes permanent diabetes. This is the minority of cases, but it is not rare enough to ignore. If you developed high blood sugar during a long steroid course, your doctor should continue monitoring your glucose even after you taper off, rather than assuming the problem simply disappears with the drug.