# Type 2 Diabetes: Step-by-Step Treatment from Diagnosis to Insulin

Type 2 diabetes (T2D) is the most common endocrine disease worldwide. According to the IDF, over 530 million people had been diagnosed by 2025, and roughly the same number remain undiagnosed. T2D is a chronic condition in which the body loses the ability to use insulin effectively (insulin resistance), and over time, to produce it in sufficient quantities. This article walks through the modern treatment algorithm step by step — from initial measures after diagnosis to insulin therapy.

T2D is driven by two parallel processes: Insulin resistance — muscle, liver, and fat cells lose sensitivity to insulin. Glucose cannot enter cells and accumulates in the blood. Beta-cell dysfunction — the pancreas compensates by increasing insulin production, but over time beta-cells "burn out" and secretion declines.

Additional mechanisms: excessive hepatic glucose production, impaired incretin secretion (GLP-1, GIP), increased renal glucose reabsorption, gut microbiome disruption. These mechanisms are targets for different classes of glucose-lowering drugs.

Diagnostic criteria (any of the following): Fasting glucose ≥7.0 mmol/L (126 mg/dL) — confirmed twice. HbA1c (glycated hemoglobin) ≥6.5% — reflects average glucose over 2–3 months. 2-hour OGTT glucose ≥11.1 mmol/L. Random glucose ≥11.1 mmol/L with classic symptoms (thirst, polyuria, weight loss).

Prediabetes (HbA1c 5.7–6.4% or fasting glucose 5.6–6.9 mmol/L) — a stage where diabetes can be prevented through lifestyle changes.

Lifestyle modification is a mandatory component at every stage of therapy and may be sufficient on its own in mild diabetes.

Nutrition. There is no single "diabetic diet." Evidence-based strategies: Mediterranean diet (reduces HbA1c by 0.3–0.5%), limiting refined sugars and fast carbohydrates, portion control, increasing fiber (≥25 g/day). Carbohydrate counting becomes important with insulin therapy.

Physical activity. 150 minutes of moderate-intensity aerobic exercise per week (walking, cycling, swimming) + 2–3 resistance training sessions. Exercise increases insulin sensitivity for 24–48 hours.

Weight loss. Losing 5–7% of body weight reduces HbA1c by 0.5–1.0%. Losing 10–15% (achievable with GLP-1 agonists) can lead to diabetes remission in some patients.

Metformin remains the starting drug for the vast majority of T2D patients. It is the only glucose-lowering agent recommended simultaneously by all major international guidelines (ADA, EASD, IDF).

Mechanism: reduces hepatic glucose production, increases tissue insulin sensitivity. Efficacy: lowers HbA1c by 1.0–1.5%. Additional benefits: no weight gain (may even reduce weight), minimal hypoglycemia risk, cardioprotective effects (UKPDS data), low cost.

Dosing: start at 500 mg once daily with meals, titrate every 1–2 weeks to target 1500–2000 mg/day (in 2–3 doses). Extended-release (XR) formulation is better tolerated. Side effects: nausea, diarrhea, flatulence — usually resolve within 2–4 weeks. Contraindications: severe renal impairment (eGFR <30 mL/min), decompensated heart failure, severe hepatic impairment.

Important: monitor vitamin B12 levels during long-term metformin use — deficiency develops in 5–10% of patients.

If HbA1c hasn't reached target (usually <7.0%) after 3 months, a second agent is added to metformin. The choice depends on comorbidities, priorities, and cost.

Empagliflozin 10–25 mg/day or Dapagliflozin 10 mg/day. Mechanism: block renal glucose reabsorption → glucose is excreted in urine. HbA1c: −0.5–0.8%. Benefits: weight loss of 2–3 kg, systolic BP reduction of 3–5 mmHg, proven cardiac and renal protection (EMPA-REG, DAPA-CKD trials). Side effects: genital fungal infections (5–10%), polyuria, rarely — diabetic ketoacidosis.

Liraglutide 1.2–1.8 mg/day (subcutaneous) or Semaglutide 0.5–1.0 mg once weekly. Mechanism: mimic incretin GLP-1 — enhance meal-stimulated insulin secretion, suppress glucagon, slow gastric emptying, reduce appetite. HbA1c: −1.0–1.5%. Benefits: weight loss 3–6 kg (semaglutide — up to 6–8 kg), cardioprotection (LEADER trial for liraglutide, SUSTAIN-6 for semaglutide). Side effects: nausea (20–30%, usually transient), diarrhea, rarely — pancreatitis.

Sitagliptin 100 mg/day. Mechanism: inhibit the enzyme that degrades endogenous GLP-1. HbA1c: −0.5–0.8%. Benefits: excellent tolerability, no hypoglycemia or weight gain, once-daily dosing. Limitation: more modest efficacy compared to SGLT2i and GLP-1 RA.

Glimepiride 1–4 mg/day or Gliclazide MR 30–120 mg/day. Mechanism: stimulate insulin secretion from beta-cells. HbA1c: −1.0–1.5%. Benefits: high efficacy, low cost, decades of clinical experience. Drawbacks: hypoglycemia risk (especially in elderly or with irregular meals), weight gain of 2–3 kg. Gliclazide MR is the preferred option (lowest hypoglycemia risk in the class).

Pioglitazone 15–45 mg/day. Mechanism: activates PPARγ nuclear receptors, enhances insulin sensitivity. HbA1c: −0.5–1.4%. Benefits: durable effect, reduction in hepatic steatosis (NAFLD). Drawbacks: weight gain, fluid retention (contraindicated in heart failure), increased fracture risk in women.

If dual therapy doesn't reach target after 3–6 months, a third agent is added. Combinations should leverage complementary mechanisms: metformin + SGLT2i + GLP-1 RA — the most potent modern combination (HbA1c reduction + weight loss + cardio/renoprotection). Metformin + sulfonylurea + SGLT2i — a cost-effective combination.

Principle: do not combine drugs with the same mechanism (e.g., two secretagogues or two incretin-based agents).

Insulin is indicated when: combination of 2–3 oral/injectable agents fails to achieve target HbA1c; with pronounced symptoms (weight loss, ketosis); when HbA1c >10% at diagnosis.

Basal insulin — the first step. Insulin glargine — long-acting, one injection daily. Starting dose: 10 units or 0.1–0.2 U/kg at bedtime. Titration: increase by 2 units every 3 days until fasting glucose <7.0 mmol/L. Metformin is continued; sulfonylurea is usually reduced or discontinued (hypoglycemia risk).

Intensification. If basal insulin at >0.5 U/kg doesn't achieve control — add bolus (prandial) insulin before the main meal or switch to premixed insulin. Alternative: basal insulin + GLP-1 agonist (reduces insulin requirement and limits weight gain).

HbA1c: <7.0% for most patients; <6.5% for younger patients without complications; <8.0% for elderly, those with severe complications, or high hypoglycemia risk. Fasting glucose: 4.4–7.2 mmol/L. 2-hour postprandial glucose: <10.0 mmol/L. Blood pressure: <130/80 mmHg. LDL cholesterol: <2.6 mmol/L (with high cardiovascular risk <1.8 mmol/L).

HbA1c — every 3 months (until target is reached), then every 6 months. Self-monitoring (glucometer) — mandatory with insulin therapy; with oral therapy — as indicated. Continuous glucose monitoring (CGM) — skin sensor showing real-time glucose; increasingly accessible and informative. Annual checkups: kidney function (eGFR, urine albumin), retinal exam, foot exam, lipid panel, ECG.

Microvascular: diabetic retinopathy (leading cause of blindness in working-age adults), nephropathy (20–30% of patients), neuropathy (tingling, pain, numbness in feet). Macrovascular: coronary artery disease, stroke, peripheral arterial disease — risk is 2–4 times higher than in the general population. Diabetic foot — microtrauma + neuropathy + poor circulation → ulcers → infections → amputations. Daily foot inspection is an essential habit.

Good news: every 1% reduction in HbA1c lowers microvascular complication risk by 25–35%.

Immediate medical attention is needed for: glucose >16.7 mmol/L with nausea, vomiting, abdominal pain (suspected ketoacidosis); severe hypoglycemia (loss of consciousness, seizures); non-healing foot wound; sudden vision deterioration; signs of urinary tract infection with fever (on SGLT2i therapy).

T2D is a marathon, not a sprint. The key to success is a stepwise approach: start with lifestyle changes and metformin, regularly assess HbA1c, and intensify therapy when needed without delay. Modern drugs (SGLT2i, GLP-1 agonists) don't just lower blood sugar — they protect the heart and kidneys. Diabetes can be controlled, and you can live a full life.

*This article is for informational purposes only and does not replace medical advice. Consult an endocrinologist before starting or changing treatment.*