Management of Hyperglycemia in Lactating Mothers
For lactating mothers with diabetes, insulin is the preferred pharmacologic agent, with metformin and second-generation sulfonylureas (glyburide, glipizide) as acceptable alternatives when oral agents are necessary. 1, 2
Insulin Therapy During Lactation
Insulin remains the gold standard for managing hyperglycemia during breastfeeding because it does not cross into breast milk in measurable amounts and poses no risk to the infant. 1, 2
Key Insulin Management Principles:
Breastfeeding substantially lowers blood glucose levels, requiring insulin-treated women to consume a carbohydrate-containing snack before or during nursing sessions to prevent hypoglycemia. 1
Total daily basal insulin requirements decrease significantly during lactation—approximately 34% lower than prepregnancy doses, with breastfeeding mothers requiring approximately 0.21 units/kg/day compared to 0.33 units/kg/day in non-breastfeeding mothers. 1, 3
Evening or late-night snacks are often necessary to prevent accelerated ketosis overnight, as lactation creates a ketogenic state. 1
The risk of hypoglycemia is substantially elevated during the first 2 weeks postpartum in breastfeeding mothers (mean 11.9 episodes vs 5.5 episodes in non-breastfeeding mothers), requiring vigilant glucose monitoring and insulin dose adjustments. 3
Oral Hypoglycemic Agents During Lactation
When oral agents are preferred or necessary:
Metformin:
- Metformin is generally considered safe during breastfeeding, though it is excreted into breast milk; limited data suggest no harmful neonatal effects, but larger safety studies are still needed. 1
- Metformin is one of the preferred agents for treating diabetes during lactation according to recent evidence. 2
Sulfonylureas:
- Glyburide and glipizide can be safely used by breastfeeding women. 1
- Second-generation sulfonylureas are generally preferred over first-generation agents during lactation. 2
- Tolbutamide (first-generation) requires close infant monitoring for jaundice if used. 4
Agents Requiring Caution:
- Newer diabetes agents (GLP-1 agonists, SGLT-2 inhibitors, DPP-4 inhibitors) require caution as they have not been adequately studied during lactation. 2
- Acarbose and thiazolidinediones (glitazones) lack sufficient safety data for breastfeeding and should be avoided until more evidence is available. 1
Nutritional Management
Energy requirements during the first 6 months of lactation require an additional 200 calories above the pregnancy meal plan, with a minimum intake of 1,800 kcal/day to meet nutritional requirements for lactation while allowing slow weight loss of 1-2 lb/month. 1
Specific Nutritional Guidelines:
Adequate energy intake with appropriate meal and snack distribution is essential to prevent ketosis during lactation. 1
Monitor for ketones in maternal urine, as acetone is excreted in breast milk and may adversely affect the infant's liver. 4
Overweight women may safely lose up to 2 kg/month without affecting milk volume. 1
Monitoring Requirements
Self-monitoring of blood glucose should include fasting glucose upon waking and postprandial measurements after each main meal, with particular attention to timing around breastfeeding sessions. 5
Target Glucose Levels:
Critical Pitfalls to Avoid
Do not assume prepregnancy insulin doses are appropriate immediately postpartum—insulin sensitivity increases dramatically with placenta delivery, and using prepregnancy doses will cause severe hypoglycemia. 1, 3
Do not use glucose-specific urine testing methods, as lactosuria (lactose in urine) may interfere with nonspecific glucose measurement methods during lactation. 4
Do not overlook the increased hypoglycemia risk during nighttime feedings—ensure adequate bedtime snacks and consider setting alarms for glucose checks during extended nursing sessions. 1
Long-Term Considerations
Women with a history of gestational diabetes who require ongoing diabetes management during lactation should undergo testing for persistent diabetes or prediabetes at 4-12 weeks postpartum using a 75-g oral glucose tolerance test, as they have a 50-70% risk of developing type 2 diabetes over 15-25 years. 1, 5