Blood contains glucose because it is an essential energy source for cells in the body. However, the kidneys normally filter out glucose from the blood and reabsorb it back into the bloodstream, so that there is no glucose present in normal urine. The presence of glucose in urine, known as glucosuria, can be a sign of diabetes or other health conditions.
If you are talking about three substances that are normally found in blood but not in urine, they are leukocytes, erythrocytes and glucose.
Glucose is not in Urine because the body transforms all the extra glucose into fat and stores in the the body instead of excreting it with urine. Glucose can be seen in urine in uncontrolled diabetes millitus, when the blood glucose level is higher than the kidneys threshold of glucose reabsorbtion, then the extra glucose gets excreted with urine instead of getting reabsorbed by the kidneys.
The malfunctioning organ that causes glucose in urine is the kidneys. Normally, the kidneys filter glucose from the blood and reabsorb it back into the bloodstream. When the kidneys are not functioning properly, they may not be able to reabsorb all the glucose, leading to its presence in the urine, a condition known as glycosuria.
A clearance value of zero for glucose means that no glucose is being excreted or removed from the body within the specified time frame. This could indicate a problem with glucose metabolism or kidney function, as glucose should normally be cleared from the body through urine.
The normal glucose concentration in urine ranges from 0 to 15 mg/dL. The glucose concentration in urine becomes zero when no glucose has spilled over into the urine.
As the number of glucose carriers increase, the concentration of glucose in the urine will decrease. This is because more glucose is being reabsorbed by the kidneys back into the bloodstream, reducing the amount of glucose that gets excreted in the urine.
Insulin affects the concentration of glucose in the urine.
Normally your body will hold on to most things that it can use and will remove those that it doesn't. If you are not making enough insulin, glucose will be found in the urine. Insulin is needed to carry the glucose molecule into the cell and if it isn't doing this, the glucose will "spill over" into the urine. Testing will give the doctor an idea if you are making insulin and perhaps you might need to take it.
Diabetic patients will more than likely have an elevated amount of Glucose in the urine. This is called glycosuria. **Elevated levels of glucose in the urine in a non diabetic pregnant woman MAY be a sign of Gestational Diabetes and should be reported to the treating physician.
All of the glucose are reabsorbed from the Proximal convoluted tubule into the surrounding capillaries,so there is no no glucose in urine.
The nephrons (filtering units in the kidney) actively reabsorb glucose from the urine. Up until a blood sugar of about 200, there should normally be no glucose found in the urine. Glucose in the urine (also called glycosuria), can be seen in diabetes and other conditions that cause an increased blood glucose. There are also some conditions that prevent the nephron from reabsorbing glucose filtered in the kidney.