Overview

Diabetes mellitus is a heterogenous metabolic disease that is defined in the Introduction section.

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The Epidemiology section gives a detailed discussion on the cases affected by diabetes mellitus regionally and worldwide.

Genetic and environmental factors that cause diabetes mellitus are found in the Etiology section. Insulin secretion defects and effects are discussed in the Pathophysiology section.

Diabetes mellitus can be classified as type 1, type 2, gestational, and other specific types. These different types of diabetes mellitus are described in the Classification section. 

History and Physical Examination

Patients with diabetes mellitus present with classic signs and symptoms that are specific to the type of diabetes the patient has. The Clinical Presentation and Physical examination sections enumerate these signs and symptoms. In the History section, the essential information that needs to be elicited from the patient to come up with the proper diagnosis and management are mentioned.

Diagnosis

Parameters to be considered in the diagnosis of diabetes mellitus are in the Diagnosis or Diagnostic Criteria section. The need for laboratory tests included in these parameters such as HbA1c level and 2-hour plasma glucose measurement are included in the discussion.

All adults who are overweight (body mass index of ≥23 kg/m2 for Asians) or with a waist circumference of ≥80 cm for Asian women and ≥90 cm for Asian men should be screened for diabetes mellitus especially with some of the risk factors mentioned in the Screening section.

The Laboratory Tests and Ancillaries section enumerates the tests that can be performed in assessing and evaluating the effect of the disease on the patient.

Other diseases that can cause persistent hyperglycemia and should be ruled out are listed in the Differential Diagnosis section.

Management

The overall target of the management for diabetes mellitus is to improve the quality of life and prevent complications and early death. In the Principles of Therapy section, the goals and factors to consider in choosing treatment in patients with diabetes mellitus is discussed.

Drugs that can be considered in the management of diabetes mellitus such as biguanides, glucagon-like peptide-1 (GLP-1) receptor agonists, sulfonylureas or insulin secretagogues, etc, and their effect in lowering HbA1c are enumerated and discussed in the Pharmacological Therapy section.

Lifestyle modification strategies, patient education and psychological therapies are essential parts of the management of patients with diabetes mellitus and are elaborated in the Nonpharmacological section.

Assessment of glycemic control is essential in evaluating the effects of therapy given to the patient and the Monitoring section explains these methods and the glycemic goals.  

The Complications section enumerates the effects of poor glycemic control in patients with diabetes mellitus. The section also discusses in detail the management of each complication.


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Frequently Asked Questions

What is first‑line therapy for type 2 diabetes?
Lifestyle modification combined with metformin is the recommended initial therapy for most patients with newly diagnosed type 2 diabetes; metformin may be continued as background therapy when adding other agents. Individualize targets and therapy based on comorbidities, hypoglycaemia risk, weight goals, access and patient preference [1].
When should insulin be started in type 2 diabetes?
Initiate insulin when there is ongoing catabolism (weight loss), symptomatic or severe hyperglycaemia, osmotic symptoms, HbA1c >10% or plasma glucose ≥16.7 mmol/L (≥300 mg/dL). Start with basal insulin to target fasting glucose, continue metformin, titrate to fasting target and escalate to basal‑bolus or add GLP‑1 receptor agonist if HbA1c remains elevated. Monitor for hypoglycaemia, adjust concomitant secretagogues, and reassess every 3–6 months. Read more
Which GLP‑1 or SGLT2 agents offer cardiorenal benefit?
For reducing major adverse cardiovascular events and improving renal or heart‑failure outcomes, prefer GLP‑1 receptor agonists with proven MACE benefit (eg, liraglutide, dulaglutide, semaglutide) and SGLT2 inhibitors proven for HF/CKD (eg, empagliflozin, dapagliflozin, canagliflozin). Use these agents in patients with established ASCVD, heart failure, or CKD (consider SGLT2 if eGFR ≥20 mL/min/1.73 m2 and UACR thresholds), independent of baseline HbA1c; choose based on patient comorbidity, tolerability and access [1].
How should hypoglycaemia be managed in practice?
Treat level‑1 hypoglycaemia with 15–20 g oral glucose or equivalent carbohydrate and recheck glucose in 15 minutes; repeat if needed. Level‑2 (glucose <3.0 mmol/L) requires prompt carbohydrate. Severe (level‑3) events need IV glucose or intramuscular glucagon; prescribe glucagon for patients at risk of severe events and train caregivers in its use. Review meds and adjust insulin or secretagogues to reduce recurrence [1].
What are effective weight‑management strategies for diabetes?
Prioritise structured lifestyle intervention (diet, physical activity, behavioural support) aiming for ≥5% weight loss. Pharmacotherapy with GLP‑1 receptor agonists or tirzepatide and SGLT2 inhibitors can substantially augment weight loss; consider metabolic/bariatric surgery for BMI ≥30 kg/m2 (≥27.5 kg/m2 Asian). Individualise treatment, monitor metabolic and renal parameters, and combine approaches for durable results [1].