U And E Blood Test Results Explained


The U and E blood test stands for the Urea and Electrolytes blood tests which is performed to assess kidney and renal function especially homeostasis and excretion. Our kidneys are essential organs that help in managing the body’s fluid balance. The tests are also used to diagnose any urinary symptoms and kidney infections one may be suffering from.

Substances such as urea and creatinine are supposed to be excreted out of the body. A rise in their presence may indicate that there is kidney damage or a disorder. Also, levels of electrolytes in the blood and the glomerular filtration rate may be used to investigate this.

Who is supposed to undertake this test?

This test is for anyone who wishes to know how his or her kidneys are functioning. This test is administered as a general health checkup or for those individuals who are taking medicine that is known to affect the kidneys. For those who already have kidney failure or any kidney-related infection, this test may be used to monitor whether any progress is being made.

How is this test performed?

Since it is a blood test, a few milliliters of your blood will be required from a vein. However, in newborn babies, blood is taken from a heel-prick sample.

Kidney Function

In order to understand the importance of this test, we have to understand the major functions of the kidneys first. The kidneys have three major functions which include, homeostasis, endocrine activity and excretion. Homeostasis involves the regulation of blood volume, maintaining pH levels and regulating levels of electrolytes such as sodium and potassium.

Endocrine activity mainly involves regulating blood pressure and supporting red blood cell production. Excretion is the removal of waste products such as urea and creatinine. Kidneys have millions of smaller units which are called nephrons. The top part of a nephron is known as the glomerulus which acts as a filter for the contents in the blood stream.

Urea and Creatinine

Urea is derived from the liver as a by-product of the biochemical metabolism activities. Creatinine is derived from the muscles as a by-product of the breakdown of proteins in the blood. These tests mainly focus on the levels of these products. These two waste products help in the excretion of excess nitrogen in our blood stream.


As stated above, this may include sodium and potassium which are secreted in our blood. Raised sodium levels may be caused by consuming a diet rich in salts or by dehydration. This can be identified by a sudden loss of elasticity on our skin.

Low blood volume is also another reason for raised sodium levels which can be as a result of excessive loss of water in urine, while sweating or diarrhea or drinking less water. Drinking more fluids is a simple treatment of this condition. Low sodium levels may be caused by the body retaining excessive amounts of water or excessive loss of water. This can be treated with thiazide drugs.

Raised potassium levels may be as a result of failure to excrete or potassium being released from damaged cells such as tumor cells during chemotherapy. This may be treated by administering insulin and glucose to get potassium into the cells. Low potassium levels are caused by excessive vomiting or diarrhea or alkalosis. Treatment is administered orally or by adding potassium via intravenous infusion.

Glomerular Filtration Rate

This is the ultimate test for whether the kidney is functioning properly. It is the rate at which blood is being filtered over the glomerulus in order to begin urine production. The glomerular filtration rate falls as one grows older, so the minimum level should be 90ml/minute/1.73m2. in the past, glomerular filtration rate was measured by taking a 24-hour sample but is now measured from one of two equations.

These two equations are; the Cockcroft-Gault equation and the MDRD formula. The former uses serum creatinine, weight, age and sex while the latter takes into account ethnicity, age, creatinine and sex. There are free online calculators which are available for the two equations. However, please consult your doctor who should carry out a laboratory test to determine which of the two is more accurate.

Kidney-related diseases

Renal disease

There are so many causes of renal diseases which may be categorized into three stages. Pre-renal disease is characterized by the following factors such as, failure of blood flow into the kidney which may be caused by renal artery stenosis or poor cardiac output which may be associated with heart failure.

True renal disease is experienced in septic shock, in renal carcinoma, in high levels of toxicity and even in traumatic damage. Post renal disease is associated with problems in the lower parts of the kidney such as the ureter or the urethra or the bladder. This may be caused by kidney stones, prostate cancer or bladder cancer. All these prevent urine flowing out which will eventually back up to the kidneys.

Chronic Kidney Disease

This is the irreversible loss of kidney function. There may be too much or too little body fluids being excreted. This is life-threatening since the patient is unable to excrete electrolytes such as potassium and sodium. There are also low levels of calcium which may occur due to the kidney losing the ability to facilitate the absorption of calcium in the intestines. This may lead to anaemia which is caused by the lack of water in the blood stream.

Urinary Tract Infection

This condition is common in women this because the urethra which removes urine from the body is close to the anus hence, any bacteria present may be introduced. If not treated, it may continue to infect the kidneys.

Having sexual intercourse may also introduce the bacteria into the urinary tract. The symptoms of this disease are, a burning sensation while urinating,you may experience pain in your lower abdominal area, feeling fatigued all the time, your urine may appear darker or may be producing a strange smell.

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