What is a good add-on medication for a patient with type 2 diabetes taking 10 units of aspart (insulin aspart) three times per day with an A1c of 13, considering affordability?

Add-On Medication for Type 2 Diabetes with Inadequate Glycemic Control on Prandial Insulin

Add metformin immediately if not already prescribed, as it is the most affordable and effective add-on medication for this patient with an A1c of 13% on insulin aspart alone. 1

Why Metformin is the Priority Add-On

Metformin should be started at the time type 2 diabetes is diagnosed and continued even when insulin therapy is initiated or intensified. 1 This patient appears to be on prandial insulin without basal insulin coverage and without metformin—a fundamentally flawed regimen that needs immediate correction.

Cost and Efficacy Profile

• Metformin has the lowest cost among all diabetes medications while providing high efficacy with A1c reductions of 0.9-1.1% when added to existing therapy. 1
• It is inexpensive, safe, and may reduce risk of cardiovascular events and death. 1
• Real-world evidence demonstrates metformin has extremely high cost-effectiveness, particularly relevant in resource-constrained healthcare systems. 2

Metformin Dosing Strategy

• Start metformin at 500-850 mg once or twice daily with meals to minimize gastrointestinal side effects. 3
• Titrate up to at least 1000 mg twice daily (2000 mg total daily dose) over 1-2 weeks as tolerated, with maximum effective doses up to 2500 mg/day. 4
• Continue metformin even when intensifying insulin therapy, as it reduces total insulin requirements and provides complementary glucose-lowering effects. 4

Critical Problem: Missing Basal Insulin Coverage

This patient is on prandial insulin only (aspart three times daily) without basal insulin—this regimen cannot adequately control fasting hyperglycemia or provide 24-hour glucose coverage. 1

Add Basal Insulin Immediately

• With an A1c of 13%, this patient requires both basal and prandial insulin coverage from the outset. 1
• Start basal insulin (NPH, glargine, detemir, or degludec) at 10 units once daily or 0.1-0.2 units/kg body weight. 1, 4
• For severe hyperglycemia (A1c ≥9%), consider higher starting doses of 0.3-0.5 units/kg/day as total daily insulin dose. 1, 4
• Increase basal insulin by 4 units every 3 days if fasting glucose ≥180 mg/dL, or by 2 units every 3 days if fasting glucose is 140-179 mg/dL, until reaching target of 80-130 mg/dL. 1, 4

Optimizing the Current Insulin Regimen

The current dose of 10 units of aspart three times daily (30 units total) is grossly inadequate for an A1c of 13%. 4

Insulin Dose Adjustment

• For A1c >10%, patients typically require 0.3-0.5 units/kg/day as total daily insulin dose, split between basal (50%) and prandial (50%) components. 1, 4
• The prandial insulin doses should be titrated by 1-2 units or 10-15% every 3 days based on pre-meal and 2-hour postprandial glucose readings. 4
• Studies show that insulin aspart at mealtimes provides better A1c reduction than NPH insulin alone when combined with metformin (A1c reduction of 2.9-3.0% vs 2.1%). 5, 6

Alternative Affordable Add-On Options (If Metformin Contraindicated)

If metformin is truly contraindicated or not tolerated, consider these affordable alternatives:

Sulfonylureas

• Low cost with high efficacy (A1c reduction ~0.9-1.1%). 1
• Major side effects include hypoglycemia risk (high) and moderate weight gain. 1
• When advancing beyond basal-only insulin to basal-bolus therapy, discontinue sulfonylureas to prevent hypoglycemia. 4

NPH Insulin as Basal Component

• NPH insulin is the most affordable basal insulin option, though it causes more hypoglycemia than long-acting analogs. 1
• Cost considerations are particularly important given substantial price increases of newer insulin products over the past decade. 1

Common Pitfalls to Avoid

• Do not delay adding metformin when initiating or intensifying insulin therapy—metformin should be continued unless contraindicated. 1, 4
• Do not continue prandial insulin alone without basal coverage—this patient needs a complete basal-bolus regimen for A1c of 13%. 1, 4
• Do not use sliding scale insulin as monotherapy—it is explicitly condemned by all major diabetes guidelines and shown to be ineffective. 4
• Do not delay treatment intensification—prolonged exposure to severe hyperglycemia (A1c 13%) increases complication risk and demonstrates clinical inertia. 1, 7

Expected Outcomes

• Adding metformin to the current insulin regimen should reduce A1c by approximately 0.6% while reducing insulin requirements. 1
• Properly implementing basal-bolus insulin therapy with metformin can achieve A1c reductions of 2-3% from current levels. 4, 5
• Triple therapy with metformin, basal insulin, and prandial insulin provides superior glycemic control compared to insulin alone. 5, 6