Relative hypoglycemia happens when your body is used to high blood glucose levels, and your blood sugar drops by about a third of its average level. You may experience typical hypoglycemia symptoms.

There’s a normal range for blood glucose, and then there’s a range of blood glucose measurements that are considered too low, resulting in hypoglycemia.

But there’s also another category of blood glucose ranges that’s more individualized based on your medical history and overall health.

Relative hypoglycemia is an often overlooked situation where your body’s threshold for symptoms and other difficulties associated with hypoglycemia is higher than usual.

This article will explore why this happens and who’s at risk.

Relative hypoglycemia is a form of hypoglycemia that occurs outside the “normal” low blood glucose ranges.

For most people without diabetes, blood glucose levels should range between 70 and 120 milligrams (mg)/deciliters (dL).

If your blood glucose is above 120 mg/dL, it can be related to whatever you ate or drank right before checking. But continued high readings could be an indication of diabetes and other forms of hyperglycemia.

When your blood glucose level drops below 70 mg/dL, hypoglycemia can occur. Clinical guidelines consider blood sugar levels at 55 mg/dL or below as severe hypoglycemia, requiring immediate treatment.

Whether your blood sugar drops from your diet and fasting, diabetes, or some other cause, low blood glucose levels can be dangerous.

You may experience hypoglycemia when your blood glucose levels drop below 80 or 90 mg/dL. In some situations, this cutoff can be even higher. This phenomenon is known as relative hypoglycemia, or the more modern term of pseudo-hypoglycemia.

Learn more about what is considered a standard range for blood glucose levels.

Relative hypoglycemia is low blood sugar that occurs at a glucose level that’s higher than what is considered normal — even for people with diabetes.

This means that while your blood glucose reading may be interpreted as “normal” at 80 mg/dL, if you have relative hypoglycemia, you could be at risk of developing difficulties from hypoglycemia at this level.

The glucose level at which you experience relative hypoglycemia can vary. For many people, it’s a drop of about 30% from their usual or average blood glucose level.

Relative hypoglycemia usually develops in people with diabetes who are experiencing severe illness.

The typical range for low blood glucose is based on the typical range for ideal blood glucose levels.

Therefore, when you’re used to maintaining a higher blood glucose on a daily basis, decreases in glucose levels — even to what is usually considered a “normal” blood sugar — can be too low for your body to handle.

The symptoms of relative hypoglycemia will look about the same as symptoms of typical hypoglycemia. This includes things such as:

  • sweating
  • shakiness
  • confusion
  • a racing heart rate
  • nausea
  • irritability or nervousness

Relative hypoglycemia can occur in people with uncontrolled diabetes who aren’t used to their blood sugar levels approaching that standard range.

But it usually develops in people who have diabetes and become critically ill.

High blood glucose levels and hemoglobin A1c levels are linked to higher mortality rates in just about everyone. But they become an even bigger problem in the setting of critical illness for both people with and without diabetes.

High blood sugar levels can develop from medications given during critical illness, or as a result of the illness itself. It’s also associated with mortality rates in people admitted to intensive care units (ICUs).

Several studies have linked the development of relative hypoglycemia in critically ill people to increased levels of delirium in the hospital setting. When glucose levels drop, neurological and psychological symptoms can be expected.

In some people, a drop of 30% from their average blood glucose levels — such as during hospitalization and treatment that requires close blood sugar management — is enough to trigger symptoms of hypoglycemia even without reaching “normal” hypoglycemia measurements.

Hypoglycemia can also develop as a complication of both neurological and psychological disorders. When any part of your body’s system for managing blood sugar levels isn’t functioning normally, hypoglycemia can occur.

Psychological issues and neurological problems that cause things such as mood changes and forgetfulness can particularly affect how well someone can maintain an effective diabetes treatment plan.

Medications designed to reduce blood sugar levels can easily be measured or administered incorrectly, especially in times when you’re not feeling well or thinking clearly. Overtreatment of a high blood glucose level by accident or even on purpose can be a complication of neurological or psychological conditions.

Relative hypoglycemia can happen for several reasons, but it can be a particular risk when uncontrolled diabetes is treated quickly to bring glucose levels down to the standard range.

Once your body becomes used to a high blood glucose level as its norm, lower levels can induce symptoms of hypoglycemia.

For this reason, some critical care healthcare professionals are calling for less strict control of blood glucose in times of severe illness.

Despite the increased risk for complications and even death in critically ill people with high blood glucose levels, some experts say that keeping blood glucose between 140 and 200 mg/dL in the ICU setting is safer than bringing people down to a “normal” range in terms of preventing other complications, such as relative hypoglycemia.

Relative hypoglycemia happens when your body is used to high blood glucose levels, and your blood sugar drops by about a third of its average level.

While these blood glucose levels might not meet the standard criteria for hypoglycemia, relative hypoglycemia can produce the same physical and psychological effects, since your body is still sensing a big change in blood sugar.

You may consult your healthcare team about the best way to manage your high blood glucose, especially if you have a high A1C and you’re at risk of severe illness. Gradually getting your average blood glucose to a more standard range can help you avoid relative hypoglycemia and other complications that could arise alongside diabetes, a critical illness, or both.