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Understanding Glycosuria

What Is Glycosuria?

Glycosuria is the presence of sugar in your urine (pee). Normally, urine contains no glucose or very little. Glycosuria is when urine tests show a clinical value of more than 0.25 milligrams (mg) of sugar per milliliter of urine (0.25 mg/mL), which may be considered pathologic, meaning it’s caused by a disease. 

The terms glycosuria and glucosuria are used interchangeably. However, they are not exactly the same. Glycosuria is the general term describing the presence of sugar in the urine, such as glucose,  galactose, fructose, or lactose. Glucosuria specifically refers to glucose in urine. In other words, glucosuria is a type of glycosuria. In fact, glucosuria is the most common type of glycosuria.

What Is The Difference Between Hyperglycemia and Glycosuria?

Hyperglycemia is a condition in which there is too much glucose (sugar) in your blood. Hyperglycemia is often called “high blood sugar.” Glycosuria is a condition in which there is too much glucose in your urine. It is often a symptom of hyperglycemia, such as in people with uncontrolled diabetes. When blood glucose levels are high, the kidneys cannot filter and reabsorb glucose back into the bloodstream, causing glucose to be eliminated through urine, resulting in glycosuria. 

Beside high blood sugar levels, kidney disease can also lead to glycosuria. In these cases, even with normal blood sugar levels, damaged kidneys prevent the filtered glucose to be properly reabsorbed back into the bloodstream, leading to high levels of glucose in the urine.  

Causes: What Causes Glucose in Urine?

There are three main causes of glucose in urine:

• Not enough insulin in your body or an inability to use insulin properly.

• High blood sugar levels.

• Kidney disorders where filtered glucose exceeds reabsorbed glucose.

Hyperglycemia and Diabetes

Insulin is a hormone made by the pancreas that regulates blood sugar levels. In people with type 1 diabetes mellitus (insulin-dependent diabetes mellitus), the pancreas does not make enough insulin. Therefore, glucose cannot enter the cell, resulting in hyperglycemia (high blood glucose levels). In people with type 2 diabetes, the body does not respond to insulin properly. Gestational diabetes is hyperglycemia that develops during pregnancy. In all types of diabetes mellitus, there is more glucose in the blood than the body can process. This leads to the elimination of glucose in urine or glycosuria. 

The renal threshold for glucose (RTG) is the blood sugar level at which the kidneys start to eliminate excess glucose in the urine. The normal RTG is around 160 to 180 milligrams per deciliter (mg/dL). However, the RTG in diabetic patients may range anywhere from 54 to 300 mg/dL. Age-related changes in the kidneys can affect the renal threshold for glucose, resulting in glycosuria in older adults.

Alimentary Glycosuria

Alimentary glycosuria is a temporary condition in which glycosuria develops after eating too many carbohydrates at once. Some glucose is eliminated through urine as the body attempts to process the carbohydrates. Blood sugar levels and urine glucose levels typically normalize within a few hours.

Familial Renal Glycosuria

Familial renal glucosuria is an inherited condition in which genetic mutations cause kidney damage, specifically in the filtration system of the kidneys called the renal tubules which are responsible for renal glucose reabsorption. The damaged renal tubule is unable to filter glucose properly, resulting in glycosuria (glucose in pee) even though the affected individual has average blood sugar levels in the normal range.

Fanconi Syndrome

Fanconi syndrome is a genetic or acquired condition in which there are problems with the proximal tubules in the kidneys. The proximal tubular cells are responsible for sodium and glucose reabsorption from the glomerular filtrate. As a result of this defect in the proximal tubule or proximal convoluted tubule, certain substances such as electrolytes (potassium, phosphorus) and glucose are eliminated from the body in urine in people with Fanconi syndrome.

Note: Fanconi syndrome is different from Fanconi anemia and Fanconi-Bickel syndrome.

Glucose-Galactose Malabsorption

Glucose-galactose malabsorption is an inherited condition in which the intestines cannot absorb the sugars glucose and galactose. Signs and symptoms include severe diarrhea, dehydration, weight loss, and mild glycosuria (glucose in pee).

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Symptoms of Glycosuria

Common Glycosuria Symptoms

• Polydipsia (excessive thirst)

• Polyphagia (excessive hunger)

• Polyuria (excessive urination)

• Dehydration (lack of enough fluids in the body)

Symptoms of Type 1 Diabetes and Type 2 Diabetes Mellitus 

• Fatigue or tiredness

• Blurred vision

• Unexplained weight loss

• Slow healing wounds

Symptoms of Renal Glycosuria

Many people with renal glycosuria are asymptomatic (no symptoms are present). When present, symptoms can include:

• Involuntary urination (enuresis) 

• Mildly delayed growth and maturation during puberty (rare) 

• Breakdown of fats (ketosis) and buildup of ketone bodies 

Symptoms of Fanconi Syndrome

• Bone pain

• Bone weakness

• Bone fractures

• Muscle weakness

• Small stature

• Low blood levels of potassium (hypokalemia) 

• Low blood levels of phosphate (hypophosphatemia)

• High levels of amino acids in urine (hyperaminoaciduria or generalized aminoaciduria)

• A buildup of acids in the body (metabolic acidosis)

How is Glycosuria Diagnosed?

Diagnostic Tests and Procedures

Some of the laboratory examinations healthcare providers do to check for glycosuria and find the underlying cause include: 

• Urinalysis: This urine test is done on a small sample of pee to measure urine glucose.

• Blood tests, such as random plasma glucose, glycated hemoglobin A1c, and glucose challenge to check for high blood glucose levels. 

Differentiating Between Causes of Glycosuria

If you have too much glucose in the urine, your healthcare professional will check your blood glucose level. This could potentially lead to a diagnosis of a condition such as type 2 diabetes mellitus. If test results show you have normal blood sugar levels and high urine glucose levels, you may have uncommon genetic conditions such as renal glycosuria or Fanconi syndrome.  A confirmed diagnosis can be made with further testing and clinical methods. 

Treatment and Management: How Do You Fix Glucosuria?

Management of Underlying Conditions

Treatment of glycosuria depends on the underlying cause. Once the underlying condition is treated, your urine glucose level should return to normal. 

How Is Glycosuria Treated?

Since glycosuria is the symptom of an underlying condition, such as diabetes or kidney disease, treatment of glycosuria involves addressing the underlying causes. For example, if you have diabetes, high blood sugar levels can lead to glycosuria. Your doctor will determine a treatment regimen that would be best for you to make sure your diabetes is under control. Medications for reducing sugars in people with diabetes and keeping glucose at the therapeutic target may include:

• Biguanides such as metformin (Glucophage, Glumetza)

• Sulfonylureas such as glipizide (Glucotrol) and glimepiride (Amaryl)

• Glucose transporters such as sodium-glucose cotransporter 2 inhibitors (SGLT2 inhibitors), for example, canagliflozin (Invokana), dapagliflozin (Farxiga), and empagliflozin (Jardiance) 

• GLP-1 (glucagon-like peptide-1) receptor agonists such as semaglutide (Ozempic) and dulaglutide (Trulicity)

• Insulin

Lifestyle and Dietary Recommendations 

• Eating a healthy diet

• Getting regular physical exercise

• Losing weight if you are overweight or obese

• Managing stress

• Quitting smoking, if you smoke

Preventing Glycosuria

It is not always possible to prevent glycosuria. For example, when glycosuria is caused by genetic defects in the kidney tubules. However, you can make lifestyle changes to lower your risk of conditions such as diabetes mellitus and gestational diabetes. 

If you have been diagnosed with type 1 diabetes, type 2 diabetes, or gestational diabetes, it’s vital that you follow the recommendations of your diabetes care team.

It’s also important for healthy people to undergo screening tests as recommended by their healthcare provider based on age and risk factors, for example, measuring fasting blood glucose levels at the time of your yearly physical and laboratory tests.