The urine is composed of a number of different substances including nutrients, salts and wastes. It is the body’s way of expelling what it does not need and maintaining a state of balance known as homeostasis. When there is any disease or disorder in the body, it may at times be detectable through changes in the composition of urine. The presence of glucose is one such abnormality.
Meaning of Sugar in Urine
Very small amounts of glucose is present in the urine under normal circumstances. It is usually trace amounts that is unlikely to be detected with tests like urine dipstick. When sugar (glucose) is detected in the urine (glycosuria) it means that sufficient amounts are present in the urine to trigger a positive result on the testing method. This is usually abnormal, especially if it is very high, persistent and not linked to any event, condition or medication.
The presence of sugar in the urine is most likely related to one of two mechanisms:
- The blood sugar levels are very high and the normally small amounts of glucose in the urine are therefore significantly higher.
- The kidney is diseased or damaged and the normal filtering of blood to form urine is malfunctioning. In this case there may be a number of abnormalities detectable in urine apart from the high glucose level.
It is also possible that the urine or testing medium could have been contaminated or tainted. While the result may be accurate, it is not indicative of an abnormality within the body.
Normal Levels and Abnormal Readings
The normal level of glucose in the urine ranges from 0 to 0.8 mmol/l (0 to 15 mg/dL). Any reading above these upper limits is considered as glycosuria. However, the specific results should be discussed with a doctor. It is also important to remember that glycosuria is not an indication of hyperglycemia. Simply, this means that high levels of sugar (glucose) in the urine does not mean that the blood sugar (glucose) levels are high.
Glucose levels in the urine can be measured with a urine dipstick test or laboratory analysis of a urine sample. The latter is more accurate. Blood glucose levels can be measured with a home glucose monitoring device or laboratory analysis of a blood sample. Similarly, the latter is more accurate. A blood test to assess glucose levels is a necessary follow up investigation when glucosuria is detected.
Causes of Sugar in the Urine
The most common causes if sugar (glucose) in the urine are usually related to raised blood glucose levels (hyperglycemia). Less commonly, kidney diseases or disorders may lead to the presence of glucose in the urine.
As the name suggest, prediabetes precedes the onset of diabetes. It is also known as glucose intolerance. The blood glucose levels are maintained within a narrow range. When it exceeds the upper end of the limit, the raised blood glucose levels are referred to a hyperglycemia.
Prediabetes is often thought of as a transition stage between normal glucose tolerance and diabetes mellitus. The raised blood glucose levels do not reach the same levels as is seen in diabetes mellitus. Unlike diabetes mellitus, prediabetes may be reversible with proper dietary and lifestyle changes.
Diabetes mellitus is one of the most common causes of glucose in the urine. In diabetes the body is unable to control the blood glucose levels causing it to elevate above the normal range (hyperglycemia). Diabetes mellitus that arises in children and younger adults is usually type 1 diabetes where there is a deficiency of insulin.
Insulin is the hormone that reduces blood glucose levels. In older adults, the problem is usually type 2 diabetes where the body becomes unresponsive to insulin (insulin resistance). Normally cells take up glucose from the bloodstream under the influence of insulin, but with insulin resistance this does not happen.
Changes in the hormone levels associated with pregnancy can also affect glucose control. It is believed that the hormones produced by the placenta blocks the action of insulin. In other words the glucose levels in the bloodstream cannot be lowered effectively.
While there may be a slight elevation of blood glucose levels after meals in pregnancy, it is usually not high enough to fall in the category of diabetes. However, some women do develop diabetes during pregnancy and this is known as gestational diabetes. In most cases it resolves a short while after child birth.
Other Causes of Hyperglycemia
There are other causes of hyperglycemia which are neither prediabetes or diabetes mellitus. These are temporary changes in glucose control and includes:
- Severe illness
- Acute stress
- Certain medication
Nephrotic syndrome is a group of symptoms seen with certain kidney diseases, autoimmune conditions, infections, cancer and with the use of certain drugs. The damage to the kidney causes a loss of protein in the urine (proteinuria), swelling (edema) and may raise the risk of other conditions. Nephrotic syndrome may also occur secondary to diabetes mellitus.
Renal glucosuria, also known as benign glycosuria, is a rare condition where the blood glucose control is normal but the kidney still passes out glucose in the urine. Usually this condition is not a problem and there are no symptoms with the benign form. The inherited form of this disease is known as familial renal glucosuria (FRG). The kidney dysfunction may also occur with a number of disorders and not only glucose reabsorption is affected.
Can consuming sugar cause glycosuria?
In a healthy person with normal glucose control, eating sugary foods or drinking sugary beverages will not cause glycosuria. The interplay of hormones like insulin will ensure that the blood glucose levels are maintained within a normal range. If the glucose is not immediately taken up by cells and used for energy, it may be converted and stored as glycogen and eventually as fat.
However, in people with impaired glucose control like in diabetes the blood glucose levels can increase with the consumption of sugar foods and drinks. This in turn can lead to an elevation of glucose levels in the urine. Other foods can also affect the blood and urine glucose levels. Unlike micro-nutrients such as vitamins, glucose is not expelled in the urine if in excess within a healthy person. Instead it is stored for later use.