Diabetes Mellitus Type 1 ✅

Related Subjects: |Diabetes Mellitus: Basics |Type 1 Diabetes Mellitus | Type 2 Diabetes Mellitus | Type 3c Diabetes Mellitus |Insulin Physiology |Gestational Diabetes |HbA1c |Hyperglycaemic Hyperosmolar State (HHS) |Diabetic Nephropathy |Diabetic Retinopathy |Diabetic Neuropathy |Diabetic Amyotrophy |Maturity Onset Diabetes of the Young (MODY) |Diabetes: Complications |Hypoglycaemia |Diabetic Ketoacidosis (DKA) Adults |Alcoholic Ketoacidosis |Euglycaemic Ketoacidosis (euDKA) with SGLT2 Inhibitors |Causes of Ketoacidosis |Gold Score: Hypoglycaemia Awareness in Type 1 Diabetes

💉 Type 1 Diabetes Mellitus (T1DM) is an autoimmune condition causing destruction of pancreatic ß-cells 🧬 → absolute insulin deficiency → hyperglycaemia. Patients require lifelong insulin to prevent ketosis and diabetic ketoacidosis (DKA ⚠️).

📖 About

• Type 1 diabetes is usually caused by autoimmune destruction of pancreatic ß-cells.
• This causes absolute insulin deficiency.
• Insulin is needed for glucose uptake into cells and suppression of ketone production.
• Without insulin, patients develop hyperglycaemia, ketosis and potentially DKA ⚠️.
• Lifelong insulin treatment is required.

🧬 Pathophysiology

• Autoimmune T-cell mediated destruction of pancreatic islet ß-cells.
• Genetic associations include HLA-DR3 and HLA-DR4.
• Low or absent C-peptide suggests reduced endogenous insulin production.
• Autoantibodies may include GAD, IA-2, ZnT8, ICA or insulin autoantibodies.
• In early disease, some patients enter a honeymoon period with temporarily reduced insulin requirements.

🩺 Clinical Presentation

• Classic symptoms: polyuria 🚽, polydipsia 💧 and weight loss ⚖️.
• Other features: tiredness, blurred vision 👁️ and recurrent infections.
• Children and young adults may present rapidly over days to weeks.
• Adults may present more slowly and can be misdiagnosed as type 2 diabetes.
• DKA may be the first presentation.

⚠️ Diabetic Ketoacidosis Features

• Nausea and vomiting.
• Abdominal pain.
• Dehydration.
• Ketotic or pear-drop breath.
• Kussmaul breathing.
• Drowsiness, confusion or reduced consciousness.
• Capillary ketones are usually raised.

💡 Important: If DKA is suspected, check ketones even if the glucose is not extremely high. DKA can occasionally occur with only modest hyperglycaemia, especially in some clinical contexts.

📊 Blood Glucose Ranges

🔎 Diagnosis

• Diagnosis is often clinical when there are typical symptoms, weight loss, ketosis or DKA.
• Blood glucose and/or HbA1c confirm diabetes.
• Check blood or urine ketones if acutely unwell or DKA is suspected.
• Islet autoantibodies can support the diagnosis if the type of diabetes is uncertain.
• C-peptide can help assess endogenous insulin production, especially if diabetes classification is unclear.

🧪 Useful Investigations

• Capillary or venous glucose.
• HbA1c for diagnosis and monitoring.
• Capillary blood ketones or urine ketones if unwell.
• U&E and renal function, especially if dehydrated or acutely unwell.
• Lipid profile and cardiovascular risk assessment.
• Urinary albumin:creatinine ratio for kidney disease screening.
• Blood pressure measurement.
• Retinal screening.
• Foot assessment.

🛠️ Management Principles

• All people with type 1 diabetes require insulin 💉.
• Oral agents must not replace insulin.
• Treatment should be individualised by the diabetes specialist team.
• Provide structured education on insulin use, carbohydrate counting, hypoglycaemia and sick-day rules.
• Encourage healthy diet, exercise, smoking cessation and cardiovascular risk reduction.
• Assess psychological wellbeing, diabetes distress and eating disorder risk.

💉 Insulin Treatment

• Basal-bolus insulin is usually preferred.
• Basal insulin provides background insulin cover.
• Rapid-acting insulin is given with meals and correction doses.
• Twice-daily mixed insulin is less flexible but may be considered if basal-bolus is unsuitable or not preferred.
• Insulin should be injected subcutaneously with rotation of injection sites.
• Injection site checks are important to detect lipohypertrophy.

📱 Glucose Monitoring & Technology

• Many patients use continuous glucose monitoring or flash glucose monitoring.
• Glucose monitoring supports dose adjustment, exercise planning and hypoglycaemia prevention.
• Insulin pumps may be considered by specialist teams for selected patients.
• Hybrid closed-loop systems may be recommended for eligible patients under NICE criteria.
• Technology choice should consider patient preference, ability to use the device, safety and local specialist guidance.

📌 NICE technology pearl: Hybrid closed-loop systems are recommended for eligible adults with type 1 diabetes if HbA1c is ≥58 mmol/mol, which is 7.5%, or if there is disabling hypoglycaemia despite best possible management with insulin pump, real-time CGM or intermittently scanned CGM. NICE also recommends hybrid closed-loop systems for children and young people with type 1 diabetes, and for people with type 1 diabetes who are pregnant or planning pregnancy, subject to implementation arrangements.

💊 Adjunctive Medication

• Insulin remains essential.
• Metformin may be considered as an adjunct to insulin in selected adults with raised BMI.
• Adjunctive medication should be started only after specialist review and shared decision-making.

🍽️ Diet & Lifestyle

• Teach carbohydrate counting to match rapid-acting insulin to meals.
• Encourage regular meals if using fixed insulin doses.
• Discuss exercise planning, including carbohydrate intake and insulin adjustment.
• Alcohol can increase hypoglycaemia risk, especially overnight.
• Smoking cessation reduces cardiovascular risk.

🧃 Hypoglycaemia

• Hypoglycaemia is usually glucose <4 mmol/L.
• Symptoms include sweating, tremor, hunger, anxiety, palpitations and confusion.
• Treat with fast-acting carbohydrate, then longer-acting carbohydrate if needed.
• Severe hypoglycaemia may require glucagon or emergency help.
• Review hypoglycaemia awareness at least annually.

🤒 Sick-Day Rules

• Never stop insulin, even if not eating.
• Check glucose more frequently.
• Check ketones if unwell or glucose is high.
• Drink fluids to avoid dehydration.
• Seek urgent medical advice if vomiting, ketones are raised, glucose remains high or DKA symptoms develop.

⏳ Complications

• Microvascular: Retinopathy, nephropathy and neuropathy.
• Macrovascular: Ischaemic heart disease, stroke and peripheral arterial disease.
• Foot disease: Neuropathy, ulcers and infection.
• Acute complications: Hypoglycaemia and DKA.
• Other: Gastroparesis, erectile dysfunction, cataracts and periodontitis.
• Psychological: Depression, anxiety, diabetes distress and eating disorders.

🧾 Annual Review

• HbA1c and individualised glycaemic targets.
• Blood pressure.
• Lipid profile and cardiovascular risk.
• Renal function and urinary albumin:creatinine ratio.
• Foot examination.
• Retinal screening.
• Injection sites.
• Hypoglycaemia awareness.
• Psychological wellbeing.
• Driving, work, contraception and pregnancy planning where relevant.

🚗 Driving Advice

• Patients using insulin must understand DVLA requirements.
• They should check glucose as advised before and during driving.
• They must not drive during hypoglycaemia.
• They should keep fast-acting carbohydrate in the vehicle.

🤰 Pregnancy

• Pregnancy should ideally be planned with specialist pre-conception diabetes care.
• Optimise HbA1c before pregnancy where safely possible.
• Use folic acid as advised pre-conception and in early pregnancy.
• Review medications for pregnancy safety.
• Urgent specialist input is needed if pregnant with type 1 diabetes.

🚩 Red Flags

• Vomiting with hyperglycaemia or ketones.
• Abdominal pain with ketones.
• Kussmaul breathing or ketotic breath.
• Drowsiness or confusion.
• Recurrent severe hypoglycaemia.
• Unexplained weight loss or persistent hyperglycaemia despite insulin.

📚 Case Example

👦 A 14-year-old boy presents with polyuria, polydipsia, weight loss and abdominal pain. He is dehydrated with Kussmaul breathing and ketotic breath. Capillary glucose is 28 mmol/L, ketones are positive and pH is 7.1. ✅ Diagnosis: Diabetic ketoacidosis due to new-onset type 1 diabetes. 🛠️ Management: urgent hospital treatment with IV fluids, fixed-rate IV insulin, potassium monitoring and later conversion to long-term subcutaneous insulin.

🧠 Exam Pearls

• Type 1 diabetes = absolute insulin deficiency.
• Think type 1 diabetes in young, lean patients with rapid onset weight loss, polyuria and polydipsia.
• Do not assume adults with new diabetes have type 2 diabetes if they are losing weight or ketotic.
• Ketones + acidosis = DKA until proven otherwise.
• Never stop basal insulin during illness.
• Basal-bolus insulin is usually the preferred physiological regimen.

📚 Summary

Type 1 diabetes is an autoimmune condition causing pancreatic ß-cell destruction and absolute insulin deficiency. Patients require lifelong insulin, education, glucose monitoring and regular complication screening. The key acute danger is DKA, while long-term care focuses on safe glycaemic control, hypoglycaemia prevention and reducing microvascular and cardiovascular complications.

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