Can Prednisone Raise A1C Levels?

Prednisone can raise A1C levels, and it does so through multiple overlapping mechanisms that push blood sugar upward for hours each day. In people already living with type 2 diabetes, even moderate doses can meaningfully shift A1C over weeks. In people without diabetes, the effect is smaller but still measurable, and prolonged courses sometimes tip a person into a prediabetic or diabetic range for the first time. The relationship between prednisone dose and A1C is real but not always straightforward, and the timing of blood sugar spikes creates some diagnostic blind spots worth understanding.

How Prednisone Pushes Blood Sugar Up

Prednisone is a glucocorticoid, a class of drugs that mimics cortisol. Cortisol’s job in the body includes mobilizing energy during stress, which partly means raising blood sugar. When you take prednisone at therapeutic doses, you’re flooding the system with far more glucocorticoid activity than the body normally produces, and the blood-sugar effects scale accordingly.

The drug works on several fronts at once. In the liver, it ramps up the production of new glucose by boosting the enzymes responsible for a process called gluconeogenesis, essentially telling the liver to manufacture more sugar and release it into the bloodstream.¹ At the same time, in muscle and fat tissue, prednisone makes cells less responsive to insulin, the hormone that normally ushers glucose out of the blood and into cells. The result is a double hit: more glucose pours in from the liver while less gets cleared by everything else.²

There’s a third layer that matters. Prednisone also impairs the insulin-producing beta cells of the pancreas. A study giving 40 mg of prednisone daily for just three days found decreased beta-cell insulin secretion in people with type 2 diabetes.³ Lab work on human islet cells tells a similar story: a prednisolone concentration matching a clinical dose as low as 5 mg per day cut glucose-stimulated insulin secretion by roughly a third.⁴ So the pancreas can’t fully compensate for the extra glucose flooding in, because prednisone is also hobbling its ability to respond.

The Afternoon and Evening Spike

One of the trickiest things about prednisone-related blood sugar rises is their timing. Most people take prednisone in the morning, and the drug’s glucose-raising effects don’t peak immediately. Instead, blood sugar tends to climb from midday onward and stay elevated through the evening. A continuous glucose monitoring study in patients on prednisolone for lung disease found that the drug predominantly causes high blood sugar in the afternoon and evening.⁵

This pattern was confirmed in a study that tracked 24-hour glucose profiles across people with normal glucose tolerance, at-risk glucose levels, and type 2 diabetes. Prednisone caused the biggest glucose increases from midday to midnight, and the effect was most dramatic in the diabetes group, where morning insulin and C-peptide levels actually dropped while afternoon and evening glucose soared.⁶

This matters for A1C because a standard fasting glucose test, drawn first thing in the morning, might look reassuringly normal while your blood sugar is running high for six or eight hours every afternoon. Fasting tests alone can miss prednisone-induced hyperglycemia entirely. A1C captures those afternoon spikes because it reflects your average glucose over roughly two to three months, but even A1C can understate the problem if the course of prednisone is short.

What the Evidence Says About A1C Specifically

The most direct evidence linking prednisone to A1C changes comes from studies tracking patients on glucocorticoid therapy over weeks to months. In a study of patients being treated for giant cell arteritis, researchers found a clear dose-dependent relationship: for every additional milligram of daily prednisone, A1C rose by about 0.018 percentage points in patients who already had diabetes and by about 0.005 percentage points in those who didn’t.⁷ That might sound small per milligram, but prednisone doses for serious inflammatory conditions often start at 40 to 60 mg a day. At 40 mg daily, the math works out to about a 0.7-point A1C increase for someone with diabetes, which is enough to shift a person from “well-controlled” into “needs a medication change” territory.

Even low-dose, long-term steroids leave a footprint. In kidney transplant recipients maintained on low-dose steroids, A1C was modestly but significantly higher than in a steroid-free control group, and the steroid group had nearly twice the risk of developing prediabetes.⁸ Among people with type 2 diabetes hospitalized for flare-ups of chronic lung disease, the total steroid dose during treatment was a significant predictor of how much A1C climbed afterward.⁹

Why A1C Can Miss or Understate the Problem

A1C reflects an average over roughly the lifespan of a red blood cell, which is about two to three months. If you take a two-week burst of prednisone for, say, a bad asthma flare, those two weeks of high blood sugar get averaged in with ten or more weeks of normal readings. The resulting A1C might tick up only slightly, even though your glucose was running dangerously high during the steroid course. In practical terms, a short prednisone taper can cause real hyperglycemia without leaving much of an A1C fingerprint.

Continuous glucose monitoring paints a more alarming picture. In patients with steroid-induced hyperglycemia being tracked by a sensor, glucose spent nearly six hours a day above the target range, with over an hour of that in a more severely elevated zone. Glucose variability, the swings up and down through the day, was about twice as high as in patients without steroid-induced glucose problems.¹⁰ These wide swings are considered harmful on their own, independent of the average glucose level. The same study noted that a metric called the glucose management indicator, which estimates an A1C-like value from 14 days of continuous sensor data, was significantly higher in the steroid-affected group and may be more useful than traditional A1C for catching acute steroid-related glucose problems.

There’s another wrinkle. A lab marker called glycated albumin, which reflects glucose control over just the past two to three weeks rather than two to three months, turns out to be artificially lowered by high-dose prednisolone. Researchers found that the prednisolone dose independently pushed glycated albumin readings down, making glucose control look better than it actually was.¹¹ So if your doctor uses glycated albumin instead of A1C to monitor your blood sugar on steroids, the test could be falsely reassuring.

People With Diabetes Versus People Without

Your starting metabolic state matters enormously. If you already have type 2 diabetes, prednisone hits harder. Your beta cells are already under strain and can’t ramp up insulin production enough to compensate. The 24-hour glucose profile studies show this clearly: people with diabetes experienced the largest glucose excursions, and their pancreatic insulin response actually got worse during prednisone treatment, not just insufficient.⁶ The dose-response relationship with A1C is about three to four times steeper in people with existing diabetes compared to those without.⁷

For people without diabetes who start prednisone, the glucose system usually has enough reserve to partially compensate, at least for a while. But “partially” is the key word. Prolonged courses or high doses can overwhelm that reserve. The kidney transplant data showed that even low doses given for maintenance immunosuppression were enough to nudge previously non-diabetic people toward prediabetes over time.⁸ Steroid-induced diabetes, sometimes called new-onset diabetes after transplant in that population, is a recognized complication with its own management challenges. It can lead to preventable hospital admissions and prolonged stays if it catches patients and providers off guard.

Does It Go Back to Normal After Stopping?

In many cases, yes, though the timeline depends on how long you were on prednisone and your underlying metabolic health. The most encouraging data comes from liver transplant recipients who were taken off prednisone after long-term use. Three out of five patients who had become insulin-dependent diabetics during prednisone therapy were able to stop insulin entirely after withdrawal, and their A1C improved. Meanwhile, a control group kept on 5 mg of prednisone daily saw no such improvement: no diabetic patients in that group became normoglycemic.¹²

For short courses, the recovery is usually faster. Once you stop the drug and it clears your system over a few days, blood sugar typically starts coming back down. But remember that A1C has a long memory. Even after glucose normalizes, A1C can take two to three months to fully reflect the improvement, because it’s still counting the glycated hemoglobin formed during the steroid course. If you get an A1C drawn two weeks after finishing a prednisone taper, it may still be elevated from the treatment period rather than reflecting your current glucose levels.

Not All Steroids Hit Equally Hard

Prednisone and prednisolone sit in the middle of the corticosteroid potency spectrum, and the degree to which different steroids raise blood sugar varies. A study comparing several oral and intravenous corticosteroids in hospitalized patients found that dexamethasone raised average blood glucose about 20 mg/dL more than prednisolone over seven days. Methylprednisolone was even worse, running about 27 mg/dL higher than prednisolone. Hydrocortisone caused the least glucose disruption.¹³

Injected steroids are a somewhat different story. A study of local corticosteroid injections in the hand and wrist of patients with diabetes found that average blood glucose increased modestly after injection, peaking at certain days but generally not reaching what the researchers considered clinically significant in most patients. Isolated big spikes did happen in the majority of participants at least once, though. If you’re getting a joint injection rather than taking daily oral prednisone, the systemic glucose effect is generally smaller and shorter-lived, but it isn’t zero, especially in the first few days.

Managing Blood Sugar While on Prednisone

If you have diabetes and need prednisone, your blood sugar management plan almost certainly needs adjusting. Because the glucose rise is concentrated in the afternoon and evening, treatments ideally need to match that timing rather than being spread evenly through the day. An intermediate-acting insulin like NPH given in the morning is one approach that has been suggested, since its peak action roughly lines up with prednisone’s peak glucose effect when both are taken in the morning.¹⁴

Several classes of diabetes medications have been tried for steroid-induced hyperglycemia. The evidence base is thin, consisting largely of case reports and small trials, but the approaches considered relatively safe given current data include metformin, DPP-4 inhibitors, and weight-based NPH insulin.¹⁴ The challenge is that steroid doses often change over the course of treatment, especially during tapers, so insulin doses may need frequent adjustment. Going from 60 mg of prednisone down to 10 mg over a few weeks means the glucose-raising effect is shrinking, and an insulin dose that was appropriate at the high end can cause dangerously low blood sugar as the steroid dose drops.

If you don’t have diabetes but are starting a longer prednisone course, monitoring your blood sugar at home, particularly in the afternoon and before dinner, can catch problems early. Many providers don’t routinely screen for glucose problems in newly started steroid patients, and the first sign of trouble might otherwise be an unexpectedly high A1C three months later or, worse, a hospital admission for severely high blood sugar.

The Appetite Factor

Prednisone is notorious for increasing appetite, and the dietary shift can compound the direct pharmacological effect on blood sugar. In a study of women given glucocorticoids for a week, food intake measured by a dietary assessment tool increased significantly by day seven, even though participants didn’t report feeling subjectively hungrier.¹⁵ Leptin, a hormone involved in satiety signaling, also rose during treatment, which would ordinarily be expected to suppress appetite. The fact that people ate more despite rising leptin suggests the appetite-driving effects of glucocorticoids operate through pathways that override the normal fullness signals.

For someone trying to keep blood sugar under control during a prednisone course, increased appetite can create a vicious cycle. The drug raises your glucose directly, and then the hunger it causes pushes you toward eating more, which raises glucose further. Being aware of this tendency is the first step. Practical strategies like planning meals in advance, keeping carbohydrate-heavy snacks out of easy reach, and focusing on protein and fiber when the hunger hits can blunt the dietary contribution to blood sugar rises, even if they can’t eliminate the pharmacological one.

When Standard Testing Fails

The gap between what’s actually happening to your glucose and what standard tests reveal can be surprisingly wide during steroid therapy. Fasting glucose misses the afternoon spikes. A1C averages away the severity of short courses. Glycated albumin can be artificially suppressed by the drug itself. This isn’t just an academic problem. Unrecognized steroid-induced hyperglycemia has been linked to longer hospital stays and higher infection risk.

Continuous glucose monitoring offers the most complete picture, capturing every spike, every hour above range, and every late-night reading that no finger stick would catch. The data showing nearly six hours a day above target range in steroid-affected patients came specifically from continuous sensors, and that level of detail simply can’t be replicated by checking glucose two or four times a day.¹⁰ If you’re on a prolonged steroid course and your provider is relying solely on morning fasting glucose to gauge the effect, you may want to ask about more comprehensive monitoring. The afternoon and evening hours are where the action is, and those are exactly the hours most testing strategies miss.