Prednisone and Hypoglycemia: An Unexpected Connection

Prednisone is one of the most widely prescribed medications in the world, and nearly everyone who takes it hears the same warning: watch your blood sugar, because it will probably go up. Hyperglycemia is indeed one of the drug’s best-known side effects. Yet a subset of people on prednisone experience the opposite problem, with blood sugar dropping low enough to cause symptoms like shakiness, confusion, and even seizures. The connection between prednisone and hypoglycemia is real, though the mechanisms behind it are less straightforward than the well-documented glucose-raising effect.

Why Prednisone Normally Pushes Blood Sugar Up

Prednisone belongs to a class of drugs called glucocorticoids, and the “gluco” in the name is a hint. These medications mimic cortisol, the hormone your adrenal glands release during stress, and one of cortisol’s core jobs is to make sure your body has enough fuel available. Glucocorticoids ramp up glucose production in the liver while simultaneously making muscle and fat tissue less responsive to insulin. The net result is more sugar entering your bloodstream and less of it being cleared out, which predictably drives blood sugar higher.¹ Research using tracer methods has confirmed that glucocorticoids significantly boost the rate at which the liver converts non-sugar precursors into glucose.²

This glucose-raising effect is so reliable that glucocorticoids have actually been used as a treatment for dangerously low blood sugar. In cases of severe, hard-to-treat hypoglycemia from insulin overdose, for instance, clinicians sometimes administer glucocorticoids specifically because they push glucose production up and slow glucose clearance from the blood.³ So the idea that a drug in this class could also cause low blood sugar sounds contradictory on its face. The explanation lies not in what prednisone does while you’re taking it, but in what happens to your body’s own hormone system around it.

How Prednisone Sets the Stage for Low Blood Sugar

The most important pathway linking prednisone to hypoglycemia runs through the adrenal glands. When you take prednisone, especially at moderate-to-high doses for more than a couple of weeks, your body registers the flood of synthetic cortisol and dials back its own production. The signaling chain that tells your adrenal glands to make cortisol, often called the hypothalamic-pituitary-adrenal (HPA) axis, gradually goes quiet. This suppression is listed among the serious complications of prolonged corticosteroid therapy.⁴

While you’re still taking the drug, this suppression doesn’t matter much because prednisone itself is filling the cortisol role. The problem emerges when you stop or rapidly reduce the dose. Your adrenal glands, having been idle, can’t immediately resume normal cortisol output. Without adequate cortisol, your liver loses a major signal to keep producing glucose, and the counter-regulatory safety net that normally catches falling blood sugar before it reaches dangerous levels stops working properly. Cortisol plays a key role in preventing hypoglycemia during times of biological stress, and when it’s absent, blood sugar can drop to symptomatic levels.⁵

This form of adrenal insufficiency is classified as iatrogenic, meaning it was caused by a medical treatment. It sits alongside autoimmune and surgical causes as one of the recognized ways the adrenal system can fail.⁵ The risk scales roughly with dose and duration: a short burst of prednisone for a week is unlikely to suppress the HPA axis meaningfully, but months of daily use at higher doses can leave the adrenals sluggish for weeks or even months after the drug is discontinued.

The Diabetes Medication Trap

A second, more immediate mechanism for prednisone-related hypoglycemia affects people who are already taking medications to lower blood sugar. If you have diabetes and start prednisone, your blood glucose will likely climb, and your doctor may increase your insulin dose or add another glucose-lowering medication to compensate. The trouble comes when the prednisone course ends. If those diabetes medication adjustments aren’t reversed promptly, you’re left on a higher dose of insulin or oral medication than your body actually needs, and blood sugar can plunge.

Corticosteroids administered by any route carry the potential for raising blood glucose, and the intensity of that rise depends on the dose, the route of administration, individual characteristics, and how long the course lasts.⁶ Clinicians are generally attentive to bumping up diabetes therapy when steroids are started. They’re sometimes less systematic about stepping it back down when steroids are tapered or stopped, and that asymmetry creates a window of vulnerability for hypoglycemia.

This isn’t just a theoretical risk. Without appropriate blood glucose monitoring and medication adjustments during and after a corticosteroid course, patients with diabetes face complications at both ends of the blood sugar spectrum.⁶ The safest approach treats both the start and the end of a prednisone course as moments requiring medication review.

The Daily Glucose Pattern on Prednisone

One of the less intuitive aspects of prednisone’s effect on blood sugar is that it doesn’t raise glucose evenly across the day. A study using continuous glucose monitoring in patients taking prednisolone (prednisone’s close pharmacological twin) for chronic obstructive pulmonary disease showed a distinctive pattern: blood sugar in the morning and overnight was often close to normal, but afternoon and evening readings climbed sharply. Among patients on prednisolone who didn’t have pre-existing diabetes, just 8 percent ever recorded a glucose reading above 200 mg/dL. But among those with known diabetes on prednisolone, that figure jumped to 53 percent, with the spikes concentrated in the hours between noon and midnight.⁷

This timing matters for hypoglycemia risk in a practical way. If a patient or their doctor sees normal fasting glucose in the morning and assumes the steroid isn’t causing problems, they may miss the afternoon spikes entirely. Conversely, if insulin doses are adjusted upward based on afternoon highs but the insulin acts during the overnight period when prednisone’s glucose-raising effect has faded, the result can be overnight lows. The mismatch between prednisone’s pharmacological timing and the timing of insulin or other diabetes drugs is one of the trickiest parts of managing blood sugar during a steroid course. Patients with diabetes taking insulin alongside prednisolone and showing normal morning glucose but elevated afternoon readings were common in the continuous monitoring data, highlighting how easily the afternoon-weighted pattern can be missed by standard fasting blood tests.⁷

Not All Corticosteroids Affect Glucose the Same Way

People sometimes assume that switching from prednisone to another steroid will solve blood sugar problems, but the picture is more complex than that. A study comparing different oral and intravenous corticosteroids in hospitalized patients found meaningful differences in how much each drug raised blood glucose. Dexamethasone and methylprednisolone were associated with greater hyperglycemia than prednisolone or hydrocortisone. Specifically, dexamethasone raised average blood glucose by about 20 mg/dL more than prednisolone across a seven-day period, and methylprednisolone raised it about 27 mg/dL more than prednisolone.⁸

Hydrocortisone, which is chemically identical to the cortisol your body makes, had the mildest glucose-raising effect of the group. This gradient matters because a drug that pushes glucose higher while you’re on it creates a steeper drop when you stop. Someone coming off a course of dexamethasone, with its longer duration of action and stronger glucose impact, faces a different adjustment curve than someone tapering off prednisolone. And the diabetes medication adjustments made to compensate for the stronger glucose-raising steroids need to be correspondingly more aggressive in the reverse direction when the steroid is discontinued.

Prednisone, Critical Illness, and a Double-Edged Sword

The hypoglycemia question becomes especially relevant in critically ill patients, where corticosteroids like hydrocortisone are frequently used to treat septic shock and other severe inflammatory conditions. In this population, both blood sugar extremes pose serious dangers. A study of hydrocortisone use in patients with cirrhosis and septic shock reported that both hypoglycemia and hyperglycemia were more frequent in the group receiving the steroid.⁹ That finding, with both highs and lows occurring more often in the treatment group, is a useful illustration of how unpredictable glucose responses can be when a powerful hormone-mimicking drug meets a body under extreme physiological stress.

In other sepsis research, hypoglycemic episodes with hydrocortisone were described as rare, suggesting that the risk varies considerably depending on the underlying condition, liver function, nutritional status, and what other drugs are on board.¹⁰ Liver disease deserves particular attention here because the liver is where most of the glucose-raising action of corticosteroids takes place. A liver that is already struggling to function may not respond to the drug’s signal to ramp up glucose production, potentially explaining why hypoglycemia can occur even while the patient is actively receiving a glucocorticoid.

Continuous Glucose Monitoring and What It Reveals

Standard blood sugar checks, whether done fasting in the morning or even a few times throughout the day, can miss the full picture of what prednisone does to glucose regulation. Continuous glucose monitoring (CGM) captures data every few minutes and reveals patterns that spot-checks would never catch. In a study of kidney transplant patients with pre-existing type 2 diabetes who were on immunosuppressive regimens including corticosteroids, CGM showed that time spent in the low range (between 54 and 69 mg/dL) increased modestly over six months, rising from 0.3 percent of readings at baseline to 0.6 percent at six months. Time spent below 54 mg/dL remained near zero throughout.¹¹

Those numbers are small in absolute terms, but the upward trend in low readings over time is telling. It aligns with what you’d expect from gradual HPA axis suppression: the longer a patient stays on corticosteroids, the more their own cortisol production may decline, and the more vulnerable they become to dips. For people without diabetes, these brief dips might never cause symptoms. For those on insulin or sulfonylureas, even small additional downward pressure on blood sugar can push them into symptomatic territory.

When Prednisone Is the Treatment for Hypoglycemia

In one of the more surprising twists, prednisone is sometimes prescribed specifically to treat a type of hypoglycemia. Insulin autoimmune syndrome, a rare condition in which the body produces antibodies against its own insulin, can cause severe and unpredictable drops in blood sugar. Because glucocorticoids suppress the immune response and reduce the production of these rogue antibodies, prednisone has been used as a treatment. In one documented case, treatment with oral prednisone at 30 mg per day, with a slow taper over two months, led to resolution of hypoglycemia and a rapid decline in insulin autoantibody levels.¹²

This dual personality of prednisone, as both a potential cause and a treatment for low blood sugar depending on context, is a good example of why the drug’s relationship with glucose can’t be reduced to a single soundbite. The same pharmacological properties that raise blood sugar in most settings can be therapeutically useful when the underlying problem is immune-mediated overproduction of insulin.

Recognizing Symptoms and Who Is Most Vulnerable

Hypoglycemia from adrenal insufficiency, whether caused by prednisone withdrawal or any other cause, can present with symptoms ranging from mild to life-threatening. Drowsiness, shakiness, feeling cold, confusion, and in severe cases seizures and collapse have all been documented as features of low blood sugar linked to adrenal insufficiency.⁵ These symptoms can be especially dangerous because they overlap with other things patients might attribute to feeling generally unwell from their underlying condition, fatigue or weakness during a disease flare, or even side effects of other medications.

Several groups face elevated risk:

People with diabetes on insulin or sulfonylureas: The combination of escalated diabetes medications during a prednisone course and the drug’s uneven daily glucose pattern creates multiple windows for lows, especially overnight and in the early morning.
Long-term steroid users who stop abruptly: Anyone who has been on prednisone for weeks to months and discontinues without a gradual taper risks adrenal insufficiency, and hypoglycemia is one of its hallmark features.
People with liver disease: Because the liver is the primary site where glucocorticoids stimulate glucose production, impaired liver function may blunt the expected glucose-raising effect and tip the balance toward lows.
Critically ill patients: The metabolic chaos of severe illness, combined with fluctuating steroid doses, erratic nutrition, and multiple interacting drugs, makes glucose swings in both directions more likely.
Children and older adults: Both groups have less physiological reserve and may show subtler signs of hypoglycemia that are easy to miss.

Practical Steps to Reduce Risk

If you’re starting a prednisone course and you have diabetes, the most important step is frequent blood sugar monitoring, ideally not just fasting but at multiple points during the day, including the afternoon and evening when prednisone’s glucose-raising effect peaks. Continuous glucose monitoring, if available, provides the most complete picture. Any increases in diabetes medication should be documented with a clear plan for stepping them back down as prednisone is tapered.

If you’ve been on prednisone for more than a couple of weeks, never stop the drug suddenly. A gradual taper gives your adrenal glands time to wake up and resume cortisol production. Even with a taper, some people experience a lag before their HPA axis fully recovers, and during that window you’re at increased risk for adrenal insufficiency and its downstream effects, including hypoglycemia. Symptoms to watch for during and after a taper include unusual fatigue, dizziness on standing, nausea, and the classic hypoglycemia symptoms of sweating, trembling, and confusion.

For people with known adrenal insufficiency from any cause, including steroid-induced suppression, patient education around “sick day rules” is considered critical. This means knowing when and how to increase your replacement steroid dose during illness or physical stress, and having access to emergency hydrocortisone injection kits for situations where oral medication can’t be taken.¹³ An adrenal crisis, where cortisol drops precipitously and blood sugar and blood pressure follow, is a medical emergency that can be fatal if not treated promptly. Recognizing hypoglycemia as a potential red flag for this condition is important for both patients and clinicians.⁵

Why This Side Effect Gets Overlooked

The reason the prednisone-hypoglycemia link surprises people is partly a framing problem. Medical education and patient information materials emphasize hyperglycemia as the glucose-related risk of steroids, and rightly so, because it’s far more common during active use. Hypoglycemia, by contrast, tends to emerge at the edges of a steroid course: during the taper, after discontinuation, or in complicated patients whose metabolic state doesn’t follow the textbook script. These are exactly the moments when medical attention may be less intense, the prescription has been completed, the follow-up appointment is weeks away, and the patient is assumed to be getting better.

The result is that many instances of steroid-related hypoglycemia probably go unrecognized or get attributed to something else entirely. A person who feels shaky and confused a week after finishing a prednisone course might assume they’re just recovering from their illness, not realizing their adrenal glands haven’t caught up yet. A patient with diabetes who has a nighttime low might blame their insulin without connecting it to the steroid taper that changed their glucose dynamics. Greater awareness of these patterns, among both patients and prescribers, could prevent a meaningful number of hypoglycemic episodes that are currently being missed.

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