Prednisone is a corticosteroid medication prescribed to manage conditions such as severe allergies, inflammatory disorders, and autoimmune diseases. The drug mimics cortisol, a hormone that suppresses inflammation and immune system overactivity. While beneficial, a temporary side effect of prednisone is its ability to increase blood sugar levels, known as hyperglycemia. This glucose elevation can occur even in individuals with no prior history of diabetes. Anyone starting this treatment should be aware of this potential change and consult with a physician about monitoring.
The Physiological Mechanism of Glucose Elevation
The process by which prednisone elevates glucose involves two primary, interconnected biological mechanisms.
Prednisone stimulates the liver to produce and release more glucose into the circulation, a process called gluconeogenesis. Acting like the stress hormone cortisol, the drug signals the liver to break down stored glycogen and create new sugar, regardless of the body’s need for energy.
At the same time, prednisone significantly impairs the effectiveness of insulin, leading to insulin resistance. Insulin allows glucose to exit the bloodstream and enter cells for energy or storage. When cells become resistant, they do not respond effectively to insulin’s signal, leaving glucose trapped in the bloodstream.
The combined effect places a dual burden on the body’s glucose regulation system: more glucose enters the circulation from the liver, and less exits to be used by the cells. For non-diabetic individuals, the pancreas attempts to compensate by producing more insulin, but this mechanism may not be sufficient to maintain normal glucose levels.
Typical Range of Blood Sugar Elevation
The magnitude of blood sugar elevation often pushes levels beyond the normal range. A healthy, non-diabetic person typically maintains a fasting blood glucose level below 100 milligrams per deciliter (mg/dL), with post-meal levels peaking below 140 mg/dL.
Studies show that after a dose of prednisone, non-diabetic patients with a normal baseline glucose around 83 mg/dL can see their levels increase significantly, sometimes reaching 140 to 183 mg/dL. This temporary elevation places readings into the pre-diabetes or mild diabetes range. The degree of the rise is closely tied to the medication’s dosage and the duration of the treatment.
The timing of the elevation is predictable, as prednisone’s effect on glucose usually peaks several hours after ingestion. For those taking the medication in the morning, the highest glucose levels are typically observed in the mid-afternoon or early evening, coinciding with lunch and dinner. This late-day peak means that fasting morning readings may remain normal, masking the drug’s true impact. Prolonged use or very high doses can lead to steroid-induced diabetes, where high glucose levels persist and require medical intervention.
Monitoring and Dietary Management
Since the glucose-elevating effect of prednisone is most pronounced after meals, monitoring should focus on post-meal checks rather than fasting values. If monitoring is recommended, checking blood sugar once daily about two hours after the lunch or evening meal is often suggested. This timing captures the period when the drug’s impact on glucose is at its height, providing a more accurate picture of the change.
Patients should be aware of common symptoms of acute hyperglycemia, such as increased thirst, frequent urination, and unexplained fatigue, and report them to their physician. If blood glucose readings consistently exceed a certain threshold, such as 216 mg/dL, the physician may recommend increasing monitoring frequency to four times a day: before all meals and at bedtime.
Dietary adjustments can help mitigate the glucose-raising effect of the medication. Reducing the intake of simple carbohydrates and refined sugars is a practical first step, as the insulin-resistant state struggles to manage rapid blood sugar spikes. Focusing on balanced meals that include lean protein, healthy fats, and high-fiber foods helps to slow down glucose absorption and minimize sharp post-meal surges. Incorporating light physical activity, such as a short walk after a meal, can also temporarily increase muscle cells’ sensitivity to insulin, helping move glucose out of the bloodstream.