Stress and Blood Glucose Levels: UK Guide

Stress glucose level blood changes are a common concern, particularly for people managing diabetes or at risk of developing it. When the body perceives stress, whether physical or psychological, it releases hormones such as cortisol and adrenaline that prompt the liver to flood the bloodstream with glucose. For most people this is a temporary response, but for those with impaired glucose regulation it can cause significant disruption. Understanding why this happens, what readings are considered normal in the UK, and when to seek medical advice can help you manage your metabolic health more effectively.

Why does stress raise your blood glucose levels?

Stress triggers cortisol and adrenaline release, causing the liver to release stored glucose while reducing insulin sensitivity, leading to elevated blood glucose levels that can persist with chronic stress.

Stress raises blood glucose levels by triggering the release of hormones, primarily cortisol and adrenaline, that prompt the liver to release stored glucose into the bloodstream. This response is part of the body's ancient "fight or flight" mechanism, designed to provide rapid energy when facing a perceived threat. Under normal circumstances, insulin then clears this extra glucose from the blood. However, when stress is prolonged or repeated, the body can struggle to keep pace with this cycle.

Both physical stress (such as illness, surgery or injury) and psychological stress (such as work pressure, bereavement or anxiety) can activate this hormonal cascade. Cortisol, in particular, also reduces the sensitivity of cells to insulin, meaning glucose is less efficiently absorbed even when insulin is present.^[1] This combination of increased glucose release and reduced insulin effectiveness can cause blood glucose to rise noticeably, though individual responses vary.

It is worth distinguishing between acute stress, which causes a short-lived spike, and chronic stress, which may sustain elevated glucose levels over weeks or months. Chronic stress is of greater clinical concern because persistently raised blood glucose can place strain on blood vessels, the kidneys and the nervous system over time. Lifestyle factors that often accompany chronic stress, including poor sleep, reduced physical activity and changes in eating habits, can compound the effect further, making stress management an important component of overall metabolic health. Diabetes UK provides accessible patient-facing information on how stress affects blood sugar and practical strategies for managing it.

Are you at greater risk if you have diabetes or prediabetes?

Yes, people with type 1 or type 2 diabetes or NDH face greater glucose disruption under stress because their compensatory insulin response is impaired or absent, making spikes more pronounced and prolonged.

People with type 1 or type 2 diabetes, or with non-diabetic hyperglycaemia (NDH), are at greater risk of significant blood glucose disruption during periods of stress because their bodies are already less able to regulate glucose effectively. In someone without diabetes, the pancreas can compensate for stress-induced glucose rises by producing more insulin. In diabetes, this compensatory mechanism is impaired or absent, so stress-related glucose spikes can be more pronounced and take longer to resolve.

For people with type 1 diabetes, the picture is complicated further because the stress response can be unpredictable. Intercurrent illness or infection most commonly raises blood glucose and increases insulin requirements in type 1 diabetes; during illness, it is important to continue insulin, monitor glucose more frequently, and check blood or urine ketones as advised by your diabetes care team (often referred to as sick-day rules).^[2] Physical exercise, by contrast, is a more typical trigger for hypoglycaemia in type 1 diabetes. Careful monitoring is therefore particularly important during stressful periods. Those using continuous glucose monitors (CGMs) may find it easier to identify stress-related patterns in their readings. CGM is routinely recommended by NICE for adults with type 1 diabetes (NICE NG17); access for people with type 2 diabetes depends on individual eligibility criteria and local NHS commissioning.^[2][3]

NDH is the preferred UK clinical term for glucose levels above the normal range but below the diagnostic threshold for diabetes. It encompasses two distinct categories: impaired fasting glucose (IFG), defined by a fasting plasma glucose of 5.5 to 6.9 mmol/L, and impaired glucose tolerance (IGT), defined by a two-hour plasma glucose of 7.8 to 11.0 mmol/L on an oral glucose tolerance test. Both categories carry an increased risk of progression to type 2 diabetes. Sustained stress-related glucose elevation may contribute to this risk, though the relationship is not fully established and individual factors vary. NICE guidance on type 2 diabetes prevention (PH38) highlights the importance of addressing lifestyle factors, including stress, as part of a broader risk-reduction strategy.^[4][5] If you have NDH and are experiencing significant or prolonged stress, discussing this with your GP or diabetes care team is advisable so that monitoring frequency and lifestyle support can be reviewed.

What blood glucose readings are considered normal in the UK?

A fasting blood glucose of 3.9 to 5.4 mmol/L is normal for UK adults without diabetes; 5.5 to 6.9 mmol/L indicates IFG, and 7.0 mmol/L or above on two occasions indicates diabetes.

In the UK, a fasting blood glucose level of 3.9 to 5.4 mmol/L is generally considered within the normal range for adults without diabetes, according to NHS and NICE reference values. A fasting plasma glucose of 5.5 to 6.9 mmol/L may indicate impaired fasting glucose (IFG), one category of non-diabetic hyperglycaemia (NDH), while a fasting level of 7.0 mmol/L or above on two separate occasions is consistent with a diagnosis of diabetes. Impaired glucose tolerance (IGT), the other NDH category, is identified by a two-hour plasma glucose of 7.8 to 11.0 mmol/L on an oral glucose tolerance test.

For HbA1c, which reflects average blood glucose over approximately two to three months, NICE defines a normal result as below 42 mmol/mol (6.0%). A result of 42 to 47 mmol/mol (6.0 to 6.4%) indicates NDH, and 48 mmol/mol (6.5%) or above is the diagnostic threshold for diabetes. These thresholds apply to diagnostic testing carried out in a clinical setting and should not be used to self-diagnose based on home readings alone. HbA1c is not suitable for diagnosis in certain situations, including pregnancy, suspected rapid-onset type 1 diabetes, haemoglobinopathies, anaemia, recent blood transfusion, or where corticosteroids may be affecting glucose levels; in these cases, plasma glucose testing is used instead.^[2]

For people already living with type 2 diabetes, NICE (NG28) recommends an individualised HbA1c target. A target of 48 mmol/mol (6.5%) is commonly used for those managed by lifestyle or metformin alone; a target of 53 mmol/mol (7.0%) may be more appropriate where there is a higher risk of hypoglycaemia, for example in those taking a sulfonylurea or insulin, or in older adults. Targets may be further relaxed depending on individual circumstances. Blood glucose targets before and after meals also vary depending on the individual's treatment plan. If you are unsure what your personal target range should be, your GP or diabetes nurse can clarify this. Home glucose monitors should be used and maintained according to the manufacturer's instructions, including performing quality control checks as advised, as readings can vary between devices.

When should you speak to your GP about stress and blood glucose?

Speak to your GP if blood glucose remains above your target range for several days, or if you develop new symptoms such as increased thirst, frequent urination or fatigue during stressful periods.

You should speak to your GP if you notice persistently elevated blood glucose readings during or after stressful periods, particularly if readings remain above your target range for several days despite your usual management. Other reasons to seek a GP appointment include new symptoms such as increased thirst, frequent urination, unexplained fatigue or blurred vision, which can indicate that blood glucose is consistently higher than normal.

If you do not have a known diagnosis of diabetes but are concerned that stress may be affecting your blood glucose, your GP can arrange a fasting glucose test or HbA1c measurement to provide a clearer picture. This is especially relevant if you have risk factors for type 2 diabetes, such as a family history of the condition, a BMI above 25 kg/m2, or a history of gestational diabetes. For some ethnic groups, including South Asian, Chinese, Black African and African-Caribbean adults, a lower BMI threshold of 23 kg/m2 or above is associated with increased diabetes risk, in line with NICE guidance (PH46).^[9][10] Early identification of NDH allows for timely lifestyle intervention, which NICE evidence supports as effective in reducing progression risk.

For people with existing diabetes, significant or unexplained changes in glucose control should always be discussed with the diabetes care team rather than managed in isolation. During illness, follow your diabetes care team's sick-day rules: continue your diabetes medication unless advised otherwise, monitor glucose more frequently, and check blood or urine ketones if glucose is persistently high. Seek same-day urgent medical assessment if you have very high glucose readings alongside ketones, vomiting, abdominal pain, rapid breathing or drowsiness, as these may indicate diabetic ketoacidosis (DKA) or hyperosmolar hyperglycaemic state (HHS). Suspected new-onset type 1 diabetes, suggested by rapid onset of thirst, frequent urination, unexplained weight loss and possible ketonuria, also requires same-day urgent assessment. If you experience symptoms of severe hypoglycaemia (such as confusion, loss of consciousness or seizures), call 999 immediately. For urgent but non-emergency concerns outside GP hours, NHS 111 can provide advice.

Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online consultations with prescriber review and pharmacist support, which may be one option for those seeking initial guidance on metabolic health alongside their NHS care. Keeping a log of your glucose readings, stress levels and lifestyle factors before your appointment will help your clinician identify patterns and tailor advice accordingly.

Frequently Asked Questions