Chemotherapy and Blood Sugar Levels: Impact and Management
Yes, chemotherapy can significantly increase blood sugar levels through multiple mechanisms, particularly when combined with glucocorticoids like dexamethasone that are commonly used as part of chemotherapy regimens. 1, 2
Mechanisms of Chemotherapy-Induced Hyperglycemia
Glucocorticoids (like dexamethasone) used during chemotherapy cause hyperglycemia through multiple pathways:
Chemotherapy regimens that include dexamethasone as an antiemetic or part of the treatment protocol are particularly associated with hyperglycemia 1, 2
All patients receiving chemotherapy for early-stage breast cancer in a recent study experienced some degree of hyperglycemia, regardless of their baseline glycemic status 2
Prevalence and Risk Factors
In a large study of 2,029 cancer patients, 16.3% experienced high blood glucose during chemotherapy (excluding those with pre-existing diabetes) 4
Patients with pre-existing diabetes or prediabetes are at significantly higher risk:
- Those with diabetes spent 73.3% of time hyperglycemic during chemotherapy
- Those with prediabetes spent 10% of time hyperglycemic
- Even patients with normal baseline glucose spent 3.9% of time hyperglycemic 2
The degree of hyperglycemia correlates directly with the steroid dose used in the chemotherapy regimen 3
Clinical Implications
Hyperglycemia during cancer treatment is associated with:
Diabetes diagnosed before or after breast cancer diagnosis is linked to poorer overall survival 1
Management Recommendations
Monitor blood glucose levels in all patients receiving chemotherapy regimens that include glucocorticoids, particularly 6-9 hours after administration when hyperglycemic effects peak 3, 1
For patients with diabetes receiving chemotherapy:
- Consider using continuous glucose monitoring to identify patterns of hyperglycemia and hypoglycemia 6
- Adjust diabetes medications based on glucose patterns observed during treatment cycles 1, 6
- Be particularly vigilant about hypoglycemia risk - one study found significant hypoglycemia risk reduction after medication adjustments guided by continuous glucose monitoring 6
For patients with high-dose dexamethasone as part of chemotherapy:
- Consider multiple-dose insulin therapy initiated at 1-1.2 U/kg per day (distributed as 25% basal and 75% prandial) for patients with blood glucose readings greater than 13.9 mmol/L (250 mg/dL) 1
- For patients without diabetes but with hyperglycemia, a single dose of isophane insulin in the morning might be appropriate 1
For patients with pre-existing diabetes on insulin therapy:
- Addition of isophane insulin (0.1-0.3 U/kg per day) to the usual insulin regimen, with doses determined according to steroid dose and oral intake, can significantly improve glycemic control 1
Nutritional Considerations
In weight-losing cancer patients with insulin resistance, increasing the ratio of energy from fat to energy from carbohydrates is recommended to:
- Increase energy density of the diet
- Reduce glycemic load 1
This approach is supported by metabolic evidence showing that while glucose uptake and oxidation are impaired in cancer patients with insulin resistance, fat utilization remains normal or increased 1
Monitoring Recommendations
All cancer patients receiving chemotherapy should have blood glucose monitored, especially those receiving regimens containing glucocorticoids 2, 1
Patients with pre-existing diabetes or prediabetes should have more intensive monitoring during chemotherapy cycles 2, 6
Educate patients about symptoms of hyperglycemia to monitor for during their treatment cycles 3
Consider referral to diabetes specialists for patients experiencing significant hyperglycemia during chemotherapy 5
By understanding and proactively managing chemotherapy-induced hyperglycemia, healthcare providers can help improve treatment tolerance and potentially outcomes for cancer patients.