Fasting with type 2 diabetes requires careful planning and medical supervision to ensure safety. Whether for religious observance such as Ramadan, or for health reasons like intermittent fasting, people with type 2 diabetes face unique risks including hypoglycaemia (low blood glucose) and diabetic ketoacidosis. The safety of fasting depends on your current diabetes control, medications, and overall health. This article explains when fasting may be appropriate, how to adjust medications safely, and what warning signs to watch for. Always consult your GP or diabetes specialist team at least 6–8 weeks before undertaking any form of fasting.

Is Fasting Safe for People with Type 2 Diabetes?

Fasting may be possible for some people with type 2 diabetes after individual risk assessment and careful planning with medical supervision. Safety depends on several factors, including the type and duration of the fast, current medications, overall diabetes control, and the presence of complications.

Key considerations for safety include:

• Current glycaemic control (HbA1c levels)

• Type of diabetes medications being taken

• Presence of complications such as cardiovascular disease or kidney problems

• Individual health status and comorbidities

People with well-controlled type 2 diabetes who are not taking insulin or certain glucose-lowering medications may fast with lower risk. However, those on insulin, sulphonylureas, or glinides face increased risk of hypoglycaemia (low blood glucose) during fasting periods. The risk of both hypoglycaemia and hyperglycaemia (high blood glucose) increases with longer fasting durations.

It is essential to consult your GP or diabetes specialist team at least 6–8 weeks before undertaking any form of fasting. A pre-fasting assessment should evaluate your current diabetes control, review your medication regimen, and identify any contraindications. Your healthcare team can provide personalised advice on whether fasting is appropriate for you and what precautions are necessary.

Certain individuals should avoid fasting altogether, including those with:

• Recent severe hypoglycaemia or diabetic ketoacidosis (DKA)

• Poor diabetes control (HbA1c >75 mmol/mol or 9%)

• Hypoglycaemia unawareness

• Advanced complications (such as severe kidney disease, heart failure, or unstable cardiovascular disease)

• Acute illness or recent hospitalisation

• Pregnancy or breastfeeding

• Frailty or cognitive impairment

The decision to fast should always be made collaboratively with healthcare professionals who understand your complete medical history. UK guidance from NICE, Diabetes UK, and the International Diabetes Federation (IDF-DAR) emphasises individualised risk stratification and structured education for people with diabetes who wish to fast, particularly during Ramadan.

Important note: Checking your blood glucose levels does not break the Ramadan fast and is an essential safety measure during fasting periods.

Types of Fasting and Their Impact on Diabetes Management

Different fasting approaches have varying effects on glucose metabolism and diabetes management. Understanding these differences helps in making informed decisions about which, if any, fasting method might be suitable.

Religious fasting is commonly practised during Ramadan, which involves abstaining from food and drink from dawn to sunset for approximately 30 days. This creates a significant shift in meal timing and can substantially affect glucose patterns. Studies have shown mixed outcomes, with some people experiencing improved glycaemic control whilst others face increased risk of hypoglycaemia or hyperglycaemia. Fasts that restrict fluids (such as Ramadan) carry higher risk of dehydration compared with fasts that allow water intake.

Intermittent fasting (IF) encompasses several patterns, including the 16:8 method (16 hours fasting, 8-hour eating window) and the 5:2 diet (normal eating for five days, restricted calories for two non-consecutive days). Some research suggests IF may improve insulin sensitivity and support weight loss in certain individuals with type 2 diabetes. However, the evidence base remains limited, with few long-term randomised controlled trials in people with type 2 diabetes, and individual responses vary considerably. Intermittent fasting is not specifically recommended by NICE as a standard diabetes management strategy; decisions should be made with your healthcare team and supported by regular blood glucose monitoring.

Time-restricted eating involves consuming all meals within a specific daily window, typically 8–12 hours, aligning eating with daytime hours. Potential metabolic effects are under investigation, and some studies indicate possible benefits for glucose control and weight management, though long-term data are still emerging.

Prolonged fasting (24 hours or more) carries higher risks for people with diabetes and is generally not recommended without close medical supervision. The extended period without food significantly increases the risk of hypoglycaemia, particularly for those on glucose-lowering medications.

Each fasting type requires different medication adjustments and monitoring strategies. The impact on diabetes management depends on individual factors, including baseline glucose control, medication regimen, and overall health status. Any fasting approach should be discussed with your diabetes team and supported by a personalised management plan.

Medication Adjustments When Fasting with Type 2 Diabetes

Medication adjustments are crucial when fasting with type 2 diabetes to prevent potentially dangerous fluctuations in blood glucose levels. Never adjust or stop diabetes medications without consulting your healthcare team first.

Medications requiring particular attention include:

Sulphonylureas (such as gliclazide, glimepiride) stimulate insulin release from the pancreas regardless of glucose levels, creating significant hypoglycaemia risk during fasting. These typically require dose reduction (often 25–50%) or temporary discontinuation, with timing aligned to eating windows. Your doctor may switch you to an alternative medication with lower hypoglycaemia risk. All adjustments must be individualised.

Insulin therapy requires careful adjustment based on the type and regimen used. Basal insulin doses often need reduction (typically around 15–30%, individualised to your circumstances), whilst rapid-acting insulin doses must be timed with meals during eating windows. People using mixed insulin preparations face particular challenges and may need to switch to a more flexible regimen temporarily. All insulin dose changes must be made under specialist supervision.

Metformin does not cause hypoglycaemia when used alone and generally does not require dose adjustment. However, timing may need modification to coincide with eating periods to minimise gastrointestinal side effects.

SGLT2 inhibitors (such as dapagliflozin, empagliflozin) carry a risk of diabetic ketoacidosis (DKA), including euglycaemic DKA (where blood glucose may be normal or only mildly elevated). This risk increases during fasting, particularly with prolonged fasts, inadequate fluid intake, acute illness, or dehydration. The MHRA advises that SGLT2 inhibitors should be interrupted during periods of prolonged fasting, surgery, or acute serious illness. If you are fasting whilst taking an SGLT2 inhibitor, ensure adequate hydration during eating windows, check blood ketones if you feel unwell or if blood glucose is persistently high, and seek urgent medical attention if ketones are elevated. Your diabetes team may recommend temporarily discontinuing these medications during extended fasting periods.

GLP-1 receptor agonists (such as semaglutide, dulaglutide) have low hypoglycaemia risk when used alone but may cause nausea and vomiting, which can be problematic during fasting and may increase dehydration risk. Dose adjustments are usually unnecessary unless combined with other glucose-lowering medications. Seek advice if gastrointestinal symptoms are persistent.

DPP-4 inhibitors (such as sitagliptin, linagliptin) and pioglitazone have low hypoglycaemia risk and may be considered as alternatives when de-escalating from sulphonylureas or insulin. However, pioglitazone can cause fluid retention and is contraindicated in heart failure.

Your diabetes team should provide a written medication plan specifying doses, timing, circumstances requiring medication omission, and advice on blood glucose and ketone testing. This plan should be reviewed well before any planned fasting period begins.

Important: If you experience side effects from any diabetes medication, report them via the MHRA Yellow Card Scheme at yellowcard.mhra.gov.uk or through the Yellow Card app.

Risks and Warning Signs to Watch for During Fasting

Fasting with type 2 diabetes carries several potential risks that require vigilance and prompt action when warning signs appear. Understanding these risks enables safer fasting practices and timely intervention when problems arise.

Hypoglycaemia represents the most immediate danger, particularly for those taking insulin or sulphonylureas. Warning signs include:

• Trembling or shakiness

• Sweating and palpitations

• Hunger and irritability

• Difficulty concentrating or confusion

• Dizziness or feeling faint

If blood glucose falls below 3.9 mmol/L, or you experience hypoglycaemia symptoms, you must break your fast immediately and treat with 15–20 g of fast-acting carbohydrate (such as glucose tablets, fruit juice, or a sugary drink). Recheck glucose after 15 minutes and repeat treatment if necessary. Contact your GP or diabetes team if hypoglycaemia occurs repeatedly. Always carry fast-acting carbohydrate with you.

Hyperglycaemia and diabetic ketoacidosis (DKA) can develop if fasting leads to inadequate medication or excessive food intake during eating periods. Warning signs include persistent blood glucose above 16.7 mmol/L, excessive thirst, frequent urination, nausea, vomiting, abdominal pain, and fruity-smelling breath. Important: DKA can occur with normal or only mildly elevated blood glucose levels in people taking SGLT2 inhibitors (euglycaemic DKA). If you are taking an SGLT2 inhibitor and feel unwell, or if blood glucose is persistently high, check blood ketones. If ketones are elevated (blood ketones ≥1.5 mmol/L), seek urgent medical attention. DKA is a medical emergency requiring immediate hospital attendance.

You should break your fast immediately if:

• Blood glucose falls below 3.9 mmol/L

• Blood glucose rises above 16.7 mmol/L

• You feel unwell or experience symptoms of hypoglycaemia or hyperglycaemia

• Blood ketones are elevated

Dehydration poses particular risk during fasts that restrict fluid intake. Symptoms include dark urine, dizziness, dry mouth, and reduced urination. Adequate hydration is essential during eating windows. Increase monitoring during hot weather or illness.

Other risks: Seek immediate medical attention (call 999 or attend A&E) for chest pain, sudden breathlessness, severe abdominal pain, persistent vomiting, confusion, or loss of consciousness.

Regular blood glucose monitoring (at least four times daily during fasting) is essential. Your diabetes team will advise on ketone testing if you are at higher risk. Understanding when to break your fast and when to seek urgent help is crucial for safe fasting.

NHS Guidance on Fasting for People with Type 2 Diabetes

The NHS recommends that anyone with type 2 diabetes considering fasting should have a thorough discussion with their healthcare team at least 6–8 weeks before the planned fast. This allows sufficient time for assessment, medication adjustments, and education.

Pre-fasting assessment should include review of recent HbA1c levels, current medications, presence of complications, and individual risk factors. NICE guidance (NICE CKS and NG28) emphasises the importance of structured education and individualised care planning for people with diabetes who wish to fast, particularly during Ramadan.

Risk stratification helps identify those at higher risk of complications. UK services commonly adopt frameworks from the International Diabetes Federation (IDF-DAR), TREND-UK, and Diabetes UK:

• Very high risk: Those with recent severe hypoglycaemia or DKA, hypoglycaemia unawareness, poor diabetes control (HbA1c >75 mmol/mol or 9%), advanced complications, acute illness, frailty, or pregnancy/breastfeeding should be advised against fasting

• High to moderate risk: Those on insulin or sulphonylureas, with moderate complications, or suboptimal control require intensive monitoring and medication adjustment

• Low risk: Well-controlled diabetes managed with diet, metformin, or low-risk medications (such as DPP-4 inhibitors or GLP-1 receptor agonists) may fast with appropriate precautions

The NHS advises regular blood glucose monitoring during fasting periods, with clear guidance on when to break the fast. Healthcare teams should provide written action plans covering medication timing and doses, blood glucose and ketone testing, warning signs, and emergency contact information.

Important: Checking your blood glucose levels does not break the Ramadan fast and is an essential safety measure.

Diabetes UK and NHS resources emphasise that fasting is a personal choice that should be respected, whilst ensuring patient safety remains paramount. Healthcare professionals should adopt a non-judgemental, supportive approach, working collaboratively with patients to minimise risks.

For those planning religious fasting, NHS diabetes teams often run specialist clinics providing culturally sensitive advice and support. Contact your GP surgery or diabetes specialist nurse to arrange a pre-fasting consultation and develop a personalised management plan that respects your wishes whilst prioritising your health and safety.

Key UK resources include:

• NICE Clinical Knowledge Summaries (CKS): Type 2 diabetes (sections on fasting and Ramadan)

• NICE NG28: Type 2 diabetes in adults: management

• Diabetes UK Ramadan guidance and resources

• IDF-DAR Practical Guidelines

• TREND-UK Ramadan resources for healthcare professionals and patients

• MHRA Drug Safety Updates (particularly regarding SGLT2 inhibitors)

Your healthcare team can direct you to these resources and provide personalised advice based on your individual circumstances.

Frequently Asked Questions