Diabetes is the most common underlying cause of kidney failure, meaning many people undergoing hemodialysis also manage diabetes with insulin. Managing blood sugar in patients with End-Stage Renal Disease (ESRD) is challenging because the kidney’s regulatory role is compromised. The dialysis process introduces rapid changes to this balance, increasing the risk of dangerous swings in blood sugar levels. Therefore, the question of whether to give insulin before a dialysis session requires a carefully considered, individualized medical answer to prevent profound hypoglycemia.
Understanding Glucose and Insulin Changes During Dialysis
The physiology of glucose and insulin is fundamentally altered in patients with advanced kidney failure, creating a high risk for blood sugar instability during dialysis. Kidneys normally clear insulin from the body, but when the glomerular filtration rate (GFR) drops significantly, this clearance is reduced. This reduced clearance prolongs the active life of injected insulin, meaning a standard dose remains active longer in the bloodstream. Consequently, patients with ESRD often require a significantly lower total daily insulin dose, sometimes reduced by 35% to 50% compared to pre-ESRD requirements.
The dialysis treatment further complicates this situation by removing glucose from the blood through the dialyzer. If a low-glucose or glucose-free dialysate is used, there is a substantial net loss of glucose from the patient, which dramatically lowers blood sugar.
Additionally, the removal of uremic toxins and the correction of metabolic acidosis during the session can temporarily improve the body’s sensitivity to insulin. This sudden increase in insulin action, combined with the loss of glucose to the dialysate, causes a rapid drop in blood sugar. This combination of reduced insulin clearance, improved sensitivity, and glucose removal makes the patient highly susceptible to hypoglycemia during and immediately after treatment.
Specific Guidelines for Insulin Administration Timing
The decision to administer insulin before dialysis depends on the type of insulin and the patient’s pre-dialysis blood glucose reading. Since dialysis lowers blood sugar, the general principle is to be conservative with insulin doses on dialysis days.
Basal (Long-Acting) Insulin
For patients receiving long-acting basal insulin, a common strategy is to reduce the dose by about 25% on the day of dialysis. This reduction mitigates the risk of hypoglycemia during the session and accounts for the prolonged action of insulin due to decreased kidney clearance. Some treatment plans recommend administering long-acting insulin only three times per week, specifically after each dialysis session, to shift the peak action away from the time of maximum glucose loss.
Bolus (Rapid-Acting) Insulin
Rapid-acting insulin is typically taken before meals, so the timing and dose must be adjusted based on the meal schedule around the dialysis appointment. If the patient will not be eating a full meal before or during the session, the mealtime bolus insulin should be significantly reduced or held entirely. If a patient eats a meal shortly before or during the session, the corresponding rapid-acting insulin dose is often reduced by 10% to 15%. All changes to a patient’s insulin regimen must be made only under the direct supervision of a nephrologist and endocrinologist.
Preventing and Treating Low Blood Sugar
Hypoglycemia, defined as a blood glucose level below 70 mg/dL, is a frequent and serious complication, occurring in up to 50% of diabetic patients on hemodialysis. Symptoms like confusion, sweating, and shaking can be misinterpreted as dialysis-related fatigue, making early detection difficult. Therefore, proactive prevention is essential for patient safety.
Prevention involves using a dialysate solution with a glucose concentration of 90 to 100 mg/dL, which minimizes the net removal of glucose from the blood. Consistent monitoring of blood glucose levels is also necessary, typically checked immediately before the session and again one to two hours into the treatment. If the pre-dialysis blood glucose level is below a certain threshold, such as 126 mg/dL (7 mmol/L), a small snack of 20 to 30 grams of low-glycemic carbohydrate is often given.
If a patient’s blood sugar drops too low during the session, the standard treatment follows the “Rule of 15.” The patient should consume 15 grams of fast-acting carbohydrate. Examples include glucose tablets, half a cup of juice, or a tablespoon of sugar. After 15 minutes, the blood glucose level is rechecked, and the 15-gram treatment is repeated if the level remains low. Once the glucose level stabilizes, the patient should consume a small snack to prevent a secondary drop in blood sugar.
Personalized Dosing and Continuous Monitoring
General guidelines provide a starting point, but the actual insulin dosage on a dialysis day must be highly individualized to the patient’s unique metabolic profile. The final dosing decision is influenced by factors such as the patient’s eating habits, pre-dialysis blood sugar readings, the specific type of dialysate used, and residual kidney function. This precision requires close collaboration between the patient and their entire medical team, including the nephrologist, endocrinologist, and dietitian.
Frequent and accurate blood glucose monitoring is necessary for patients on this therapy. Monitoring should occur before, during, and after the dialysis session to identify individual patterns of glucose fluctuation and allow for proactive dose adjustments. Continuous Glucose Monitoring (CGM) systems are recommended for this population. CGM provides real-time data that can alert the care team to asymptomatic drops in blood sugar, which are common and often missed with traditional finger-stick tests.