Kidney failure is a condition where the kidneys lose their ability to effectively filter waste and regulate substances in the body. Hypoglycemia, or low blood sugar, is defined by a plasma glucose concentration that falls below the normal range, typically considered less than 70 milligrams per deciliter (mg/dL). The direct answer to whether kidney failure causes low blood sugar is yes; kidney dysfunction significantly increases the risk of hypoglycemia. This risk is dramatically higher in patients who also have diabetes, but the underlying mechanisms contribute to this metabolic imbalance even in non-diabetic individuals.
Why Kidney Failure Disrupts Blood Sugar Control
The kidneys play a significant role in maintaining stable blood glucose levels. One primary function lost during renal failure is the kidney’s ability to produce new glucose through a process called gluconeogenesis. During periods of fasting, the kidneys normally contribute a substantial portion—up to 20 to 25%—of the body’s total endogenous glucose production.
When kidney function declines, this compensatory mechanism is compromised, leaving the body less capable of raising blood sugar to counteract a drop. The liver is the other main site of glucose production, but the loss of the kidney’s contribution means the body’s overall ability to respond to a hypoglycemic event is severely impaired. This makes patients with kidney failure much more susceptible to low blood sugar episodes.
Another major physiological function of the kidney that impacts blood sugar is the clearance of insulin from the bloodstream. The kidneys are responsible for removing or degrading a significant amount of the circulating insulin. When kidney filtration capacity decreases, insulin remains in the circulation for an extended period, leading to a prolonged and intensified effect.
This reduced insulin clearance causes blood sugar to drop lower and stay low longer than it would in a person with healthy kidneys. This mechanism applies to both the natural insulin produced by the body and the injected insulin used by many people with diabetes. Consequently, as kidney function worsens, the existing dose of insulin or other diabetes medication becomes increasingly potent.
Medication Management
The interaction between declining kidney function and diabetes medication is often the most direct cause of severe hypoglycemia in these patients. Many oral medications used to treat diabetes, as well as injected insulin, are excreted or metabolized by the kidneys. As the kidneys fail, these drugs accumulate in the body, magnifying their blood-sugar-lowering effect.
The class of oral medications known as sulfonylureas, which stimulate insulin release from the pancreas, poses a high risk. Drugs like glibenclamide or glyburide have active metabolites that rely heavily on renal excretion. When kidney function is poor, these active breakdown products build up, causing a sustained reduction in blood sugar.
Similarly, the dose of prescribed insulin must often be reduced as kidney function declines. The impaired clearance of insulin means that the same dose that was previously effective can now lead to severe hypoglycemia. Some newer classes of diabetes drugs, such as certain Dipeptidyl Peptidase-4 (DPP-4) inhibitors, also require dose adjustments based on the estimated Glomerular Filtration Rate (eGFR) to prevent accumulation.
Precise medication adjustment underscores the importance of a coordinated medical approach. Physicians, often a nephrologist and an endocrinologist, must work together closely to monitor kidney function and adjust diabetes treatment plans. Failing to proactively reduce medication doses as renal impairment progresses is a common factor leading to preventable hypoglycemic crises.
Identifying and Responding to Hypoglycemia
Recognizing the signs of low blood sugar is important for patient safety, especially since kidney failure can change the way symptoms appear. Typical initial warning signals, triggered by the release of stress hormones, include:
- Trembling
- Sweating
- A rapid or pounding heartbeat
- Intense hunger
However, in patients with advanced kidney failure, especially those with long-standing diabetes, these warning signs can be diminished or absent. A condition called autonomic neuropathy, a complication of chronic kidney disease, can blunt the body’s usual hormonal response to a drop in glucose. This absence of early symptoms makes the detection of low blood sugar much more challenging.
Instead of the typical physical warnings, the patient may move directly to neuroglycopenic symptoms, which are a result of the brain being starved of glucose. These symptoms include confusion, slurred speech, clumsiness, difficulty concentrating, or unusual behavior. Any sudden change in mental status in a patient with kidney failure should immediately raise suspicion of hypoglycemia.
Immediate action is necessary if blood sugar drops below 70 mg/dL. The standard immediate treatment is often referred to as the “Rule of 15s,” which involves consuming 15 grams of a fast-acting carbohydrate, such as glucose tablets or half a cup of juice. After waiting 15 minutes, the blood sugar level should be retested, and if it remains low, the process is repeated. If the individual is unconscious or unable to safely swallow, emergency medical services must be called immediately, and a pre-prescribed glucagon injection may be required to raise the blood sugar rapidly.