Prednisone and Blood Glucose: Risks and Management

Prednisone and blood glucose are closely linked: corticosteroids such as prednisone are well recognised to raise blood sugar levels, sometimes significantly. This happens because prednisone stimulates the liver to release and produce glucose while simultaneously reducing the body's sensitivity to insulin. The effect, known as steroid-induced hyperglycaemia, can affect anyone taking prednisone but is particularly important for people with existing diabetes or known risk factors. Understanding why this happens, how to monitor for it, and when to seek medical advice can help you manage your health safely during a course of treatment.

Why does prednisone raise your blood sugar levels?

Prednisone raises blood sugar by stimulating hepatic glucose production and reducing insulin sensitivity in muscle and fat cells, a predictable pharmacological effect of all corticosteroids.

Prednisone raises blood sugar levels by interfering with the way the body produces and responds to insulin, the hormone responsible for moving glucose from the bloodstream into cells. Prednisone is a corticosteroid, a class of medicine that mimics the effects of cortisol, a naturally occurring stress hormone. When cortisol or a synthetic equivalent such as prednisone is present in elevated amounts, it acts on the liver and on muscle and fat cells in two distinct ways: it stimulates the liver to break down stored glycogen and release glucose into the blood (glycogenolysis), and it also drives the liver to manufacture new glucose from non-carbohydrate sources such as amino acids (gluconeogenesis). At the same time, it reduces the sensitivity of muscle and fat cells to insulin (peripheral insulin resistance).^[6][7] The combined result is that more glucose enters the bloodstream while less is cleared from it.

This effect is sometimes described as steroid-induced hyperglycaemia or steroid-induced diabetes. It is not a sign that the medicine is failing or that something has gone wrong; it is a predictable pharmacological consequence of how corticosteroids work. The degree of elevation tends to follow the dose and the timing of the dose. UK clinical guidance, including that from the Joint British Diabetes Societies (JBDS), notes that blood glucose often peaks in the afternoon and evening when a corticosteroid is taken as a single morning dose, because the drug's peak activity coincides with the period of greatest insulin resistance.^[3]

It is worth noting that prednisone itself is a prodrug: it is converted in the liver to prednisolone, which is the active form.^[8][1] In UK clinical practice, prednisolone is the more commonly prescribed oral corticosteroid, but the blood glucose effects are the same because prednisone and prednisolone are pharmacologically equivalent in this respect. Both terms are used, and the monitoring and management principles described in this article apply equally to both. Understanding this mechanism helps explain why monitoring and, in some cases, medication adjustment are necessary during a course of corticosteroid treatment.

How much can prednisone affect blood glucose readings?

The rise in blood glucose depends on dose, duration, and individual metabolic health; high doses can push readings into the diabetic range, while low short-term doses may cause only modest changes.

The magnitude of the blood glucose rise caused by prednisone varies considerably depending on the dose, the duration of treatment, and the individual's underlying metabolic health. In people without any pre-existing glucose abnormality, short courses of low-dose prednisone (for example, 5 to 10 mg daily) may cause only modest and transient rises that remain within or just above the normal range. Higher doses, such as 40 mg or more daily, can push blood glucose readings substantially above normal, sometimes into ranges that meet the diagnostic threshold for diabetes (a fasting glucose of 7.0 mmol/L or above, or a random glucose of 11.1 mmol/L or above, as defined by NICE and Diabetes UK). These dose examples are illustrative; the actual effect in any individual will depend on their personal risk factors and the specific steroid regimen.

In people who already have type 2 diabetes or impaired glucose tolerance, the same dose of prednisone can cause a much larger proportional rise. It is not uncommon for well-controlled diabetes to become temporarily difficult to manage during a course of corticosteroids, with readings that were previously stable rising significantly above target range.

The pattern of elevation is also characteristic: because prednisone is typically taken in the morning, blood glucose tends to be highest in the afternoon and evening, while fasting morning readings may appear relatively normal. This means that a single fasting glucose measurement can underestimate the true extent of steroid-induced hyperglycaemia. JBDS guidance recommends checking blood glucose at multiple points during the day, particularly around two hours after the main meal, to get an accurate picture of how prednisone is affecting an individual's readings.^[3] It is also worth noting that a diagnosis of diabetes should not be made on the basis of a single elevated reading taken during a course of steroids; repeated measurements and clinical judgement are needed, and your GP or diabetes team can advise on the appropriate approach.

Who is most at risk of steroid-induced high blood sugar?

People with pre-existing type 2 diabetes or impaired glucose tolerance are at highest risk, but older age, obesity, South Asian or Black African heritage, and high prednisone doses also increase risk.

People with pre-existing type 2 diabetes or impaired glucose tolerance (sometimes called non-diabetic hyperglycaemia, or prediabetes) are at the highest risk of clinically significant steroid-induced hyperglycaemia, as their glucose-regulating mechanisms are already compromised before prednisone is introduced. However, steroid-induced hyperglycaemia can also occur in people with no prior history of diabetes, particularly when certain risk factors are present.

Key risk factors include:

• Older age, as insulin sensitivity naturally declines with age

• Overweight or obesity, particularly central (abdominal) adiposity

• A family history of type 2 diabetes

• Ethnicity, with people of South Asian, Black African, or Black Caribbean heritage at higher baseline risk of type 2 diabetes^[9]

• High or prolonged doses of prednisone, including doses above 20 mg daily or courses lasting more than a few weeks (this threshold is based on JBDS guidance on steroid-induced hyperglycaemia)

• Use of other medicines that affect glucose, such as some antipsychotics or immunosuppressants

• Gestational diabetes in a previous pregnancy

People receiving high-dose intravenous corticosteroids in hospital are also at significant risk and are typically monitored closely by clinical staff. For those in the community starting a course of oral prednisone, it is important to inform the prescribing clinician of any of the above risk factors so that appropriate monitoring can be arranged. JBDS guidance on the management of hyperglycaemia with steroid therapy supports proactive identification of people at risk of steroid-induced hyperglycaemia in primary care settings, and Diabetes UK provides accessible information on risk factors for people who want to understand their personal risk.

How to manage blood glucose safely while taking prednisone

Safe management requires a monitoring plan agreed with a GP or diabetes team, lifestyle adjustments to reduce refined carbohydrate intake, and medication changes only under clinical supervision.

Managing blood glucose safely during prednisone treatment involves a combination of monitoring, lifestyle measures, and, where necessary, medication adjustment under medical supervision. The first step is to establish a clear monitoring plan with a GP or diabetes team before or at the start of treatment, particularly for anyone with known diabetes or significant risk factors.

For people without diabetes, the GP may recommend periodic blood glucose checks during longer or higher-dose courses. For people with existing diabetes, more frequent self-monitoring is usually advised, and the diabetes care team may need to adjust insulin doses or oral medication to account for the steroid effect. It is important never to adjust diabetes medication independently without clinical guidance, as this carries a risk of hypoglycaemia, particularly if the prednisone dose is later reduced or stopped. People with type 1 diabetes and those on insulin should follow their sick-day rules and check blood ketones if glucose remains persistently elevated or if they feel unwell; their diabetes team can advise on specific thresholds and actions.

Lifestyle measures that can help moderate the glucose rise include:

• Reducing intake of refined carbohydrates and sugary foods and drinks, particularly in the afternoon and evening when steroid-induced glucose peaks are most pronounced

• Maintaining regular physical activity where health permits, as exercise improves insulin sensitivity

• Eating regular, balanced meals rather than large, carbohydrate-heavy portions

• Staying well hydrated

For people who develop significant hyperglycaemia during treatment, a GP may consider initiating short-term glucose-lowering therapy. JBDS community guidance provides thresholds to help clinicians decide when to escalate monitoring or start treatment; as a general principle, readings that are consistently and substantially above your usual target range, or any reading accompanied by symptoms, should prompt same-day contact with your GP or diabetes team. If the surgery is closed, NHS 111 can advise on whether out-of-hours assessment is needed.

Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online consultations with prescriber review and pharmacist support, and is one option for people seeking clinical guidance on managing medicines during a course of treatment. Any changes to diabetes management should always be made in partnership with a qualified clinician. The timing of the steroid dose should not be changed without prescriber advice.

Side effects to watch for and when to seek urgent help

Symptoms of high blood glucose include thirst, frequent urination, and fatigue; DKA or HHS symptoms such as vomiting, confusion, or rapid breathing require immediate 999 or A&E attendance.

Steroid-induced hyperglycaemia can sometimes develop without obvious symptoms, which is why monitoring is important rather than relying on how a person feels. However, when blood glucose rises significantly, symptoms may include increased thirst, passing urine more frequently than usual, fatigue, blurred vision, and headaches. These symptoms should prompt a blood glucose check if a monitor is available, and contact with a GP if readings are consistently elevated or if symptoms are new and unexplained.

More serious complications can arise if very high blood glucose is left unaddressed. Diabetic ketoacidosis (DKA), though more common in type 1 diabetes, can occasionally occur in people with type 2 diabetes or steroid-induced diabetes under significant physiological stress.^[11] Symptoms of DKA include nausea, vomiting, abdominal pain, rapid breathing, and confusion. Adults with type 2 diabetes are also at risk of hyperosmolar hyperglycaemic state (HHS), a serious condition caused by very high blood glucose and severe dehydration. Warning signs of HHS include extreme thirst, passing large amounts of urine, drowsiness, and confusion, which may develop gradually over several days. If any of these symptoms occur, call 999 or go to the nearest accident and emergency department immediately, as both DKA and HHS are medical emergencies.

For less urgent concerns, such as blood glucose readings that are higher than usual but not accompanied by severe symptoms, contact your GP in the first instance. If the surgery is closed and you need prompt advice, NHS 111 can provide guidance.

Suspected side effects from prednisone, including unexpected changes in blood glucose, can be reported to the Medicines and Healthcare products Regulatory Agency (MHRA) via the Yellow Card scheme at yellowcard.mhra.gov.uk. Reporting helps the MHRA monitor the safety of medicines in real-world use. People taking prednisone as part of a clinical trial should report adverse events to the trial team under the study protocol.

Does blood sugar return to normal after stopping prednisone?

Blood glucose usually returns to normal within days to weeks of stopping prednisone in people without pre-existing diabetes, but follow-up fasting glucose and HbA1c testing is recommended for those who developed hyperglycaemia during treatment.

For most people without pre-existing diabetes, blood glucose levels do return to normal after prednisone is stopped, typically within a few days to a couple of weeks as the drug clears the body and insulin sensitivity is restored. The timeline depends on the dose and duration of the course: a short five-day course at a moderate dose is likely to resolve quickly, whereas a prolonged course at high doses may take longer for glucose levels to normalise.

For people who developed steroid-induced diabetes during treatment, the picture is more nuanced. A proportion of these individuals will find that their blood glucose returns to normal once the steroid is withdrawn, suggesting that the prednisone unmasked a latent vulnerability rather than causing permanent damage. However, a significant minority will go on to have persistently elevated glucose, meeting the criteria for type 2 diabetes, even after the steroid is stopped.^[15] This is more likely in people who had undiagnosed impaired glucose tolerance before treatment began.

For this reason, JBDS guidance recommends follow-up blood glucose testing after a course of corticosteroids in people who developed hyperglycaemia during treatment. A fasting glucose test can be arranged by the GP relatively soon after stopping prednisone, while an HbA1c test (which reflects average blood glucose over approximately two to three months) is usually most informative when checked around three months after stopping, or as advised by the clinician.^[13] Together, these tests can confirm whether glucose has returned to normal or whether ongoing management is needed.

It is also important not to stop prednisone abruptly without medical advice, as sudden withdrawal can cause adrenal insufficiency, a separate and serious condition.^[5][14] Any reduction in dose should follow the tapering plan agreed with the prescribing clinician, even if blood glucose appears to have improved. NHS guidance on prednisolone and the BNF both support a gradual, supervised reduction in dose.

Scientific References

1. Prednisolone 5mg Tablets – Summary of Product Characteristics.
2. Blood glucose management | Type 2 diabetes in adults (NG28).
3. Steroid treatment and blood glucose levels.
4. Prednisolone | Drugs | BNF – NICE.
5. Corticosteroids, general use | Treatment summaries – BNF.
6. Regulation of Glucose Homeostasis by Glucocorticoids.
7. [New insights in steroid diabetes]. Acta Medica Croatica.
8. Studies on the biological conversion of prednisone to prednisolone.
9. Referring people at high risk of type 2 diabetes (QS167).
10. Abnormalities in Glucose Regulation During Antipsychotic Treatment.
11. Steroid-Induced Diabetic Ketoacidosis: A Case Report and Review of the Literature.
12. Management of Hyperosmolar Hyperglycaemic State (HHS).
13. HbA1c | Information for the public | Type 1 diabetes in adults (NG17).
14. Iatrogenic Cushing's Syndrome and Fatal Adrenal Crisis Following Systemic Corticosteroid Therapy: A Case Series of Five Patients.
15. Prednisone use, disease activity and the occurrence of hyperglycaemia and diabetes in patients with early rheumatoid arthritis: a 10-year subanalysis of the BeSt study.

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