Waste product tests are a group of blood tests that measure the levels of specific waste products (natural byproducts of metabolism) in the blood. An abnormal waste product test can signal such conditions as heart failure or kidney failure.

Before a waste product test, patients are usually ordered to fast for four to eight hours. They may also be ordered to reduce or stop taking some of their medications or vitamins because some substances can interfere with the results of the test. Patients must inform their physician of all medications and vitamins that are currently being taken.

Waste product tests are a group of blood tests that measure the levels of specific waste products (natural byproducts of metabolism) in the blood. These tests are frequently ordered as part of a basic or complete metabolic panel (BMP or CMP). This information is vital in assessing whether certain body functions are working as they should, especially the kidneys, which are responsible for eliminating these waste products from the body through the urine.

The three waste products most commonly tested for in the blood are:

Waste product testing is performed to diagnose a new condition or monitor an existing condition. Regular testing may be required for some people, including those with kidney disease and those on very high protein diets. In addition, the tests may be ordered when a CAT scan is planned or when a patient is using certain drug therapies.

Many factors may affect waste product test results, including pregnancy and recent injury or illness. Physicians will usually order patients not to eat for four to eight hours before the test. Patients should follow their physician’s restrictions on diet, exercise and medication use prior to the test.

Creatinine levels may be increased by certain drugs, such as antibiotics and powerful chemotherapy drugs (e.g. cisplatin). Creatine levels are related to muscle mass, however, moderate exercise typically will not raise creatinine levels. Creatine is now available as a dietary supplement and levels may be higher with its use. Patients should inform their physicians of any dietary supplements that are being used as they can affect the test results.

Uric acid levels may be increased or decreased by a number of factors such as:

• Alcohol. These beverages slow down the removal of uric acid in the body.
  
  
• Aspirin (and other salicylates). Low aspirin levels can cause high uric acid levels while higher doses tend to lower uric acid in the blood.
  
  
• Caffeine
  
  
• Certain medications that treat Parkinson’s disease  and asthma
  
  
• Diuretics and thiazide drugs. These medications promote urine production in the kidneys and can raise uric acid levels.
  
  
• Epinephrine
  
  
• High-protein diet. Certain foods can particularly raise uric acid levels, including organ meats (e.g., kidneys, liver), sardines and anchovies.
  
  
• Fasting or starvation diets
  
  
• Strenuous exercise
  
  
• Vitamin C
  
  
• Estrogen

BUN levels may be affected by:

• Analgesics. Pain relievers.
  
  
• Antibiotics. Medications that harm or kill microorganisms and are commonly used to treat infections.
  
  
• Antidiabetics. Medications that stimulate the production of insulin in the pancreas or improve insulin resistance for treatment of patients with adult onset diabetes.
  
  
• Antituberculars. Medications used in the treatment of tuberculosis.
  
  
• Aspirin (in high doses). Typically used as a pain-reliever (analgesic) but also reduces inflammation and inhibits the formation of blood clots (anticoagulant).
  
  
• NSAIDs (nonsteroidal anti-inflammatory drugs).
  
  
• Certain medications that treat Parkinson’s disease.
  
  
• Chemotherapy. Medications used in the treatment of cancer.
  
  
• Narcotics.
  
  
• Thiazide and loop Diuretics. Medications that promote the formation of urine in the kidneys, causing the body to flush out fluids and minerals.
  
  
• Ulcer medications.
  
  
• Vitamin C.

Waste product levels are measured in milligrams per deciliter (mg/dL). Values may vary slightly from lab to lab. Normal ranges can vary among individuals, however, general normal levels are as follows:

• Creatinine.
  Males:  0.6 to 1.2 milligrams per deciliter (mg/dL)
  Females:  0.5 to 1.1 milligrams per deciliter (mg/dL)
  
  These levels may be higher in more muscular men or middle-aged adults. Elderly individuals may have levels lower than the general population.
  
  
• Uric acid.    
  Males: 3.0 to 7.0 mg/dL
  Females: 2.3 to 6.0 mg/dL
  
  
• Blood urea nitrogen (BUN). Normal levels are 6.0 to 20 mg/dL, but may be slightly higher in elderly patients.

An abnormal waste product test may indicate a wide variety of conditions, including:

• Kidney (renal) failure. Acute renal failure is the sudden loss of the kidney’s ability to rid the body or urine and waste and conserve electrolytes.
  
  
• Heart failure. A serious condition in which the heart is not pumping well enough to meet the body’s demand for oxygen. It is called heart failure because the heart is failing to pump efficiently, which often results in congestion in the lungs.
  
  
• Liver failure. When the liver begins damaged beyond repair and the organ is not longer able to function.
  
  
• Gout. A painful joint inflammation caused by an excessive amount of uric acid in the blood and deposits of urates in and around the joints.
  
  
• Malnutrition. Inadequate nutrition that may be caused by an unbalanced diet or malabsorption, which is a condition in which the body has difficulty digesting or absorbing nutrients from food.
  
  
• Dehydration. Too little fluid in the body.
  
  
• Overhydration. Too much fluid in the body.
  
  
• Heart attack. An event that results in permanent heart damage or death. It is also known as a myocardial infarction, because part of the heart muscle (myocardium) may literally die (infarction).
  
  
• Alcoholism.
  
  
• Urinary tract obstruction (e.g., stones, tumor).
  
  
• Lead poisoning.
  
  
• Nephrotic syndrome. A grouping of findings that include protein in urine, low blood protein and swelling (edema) that often produces an increase in cholesterol levels.
  
  
• Muscular dystrophy. A progressive disease characterized by the deterioration of muscle.
  
  
• Gigantism or acromegaly. Excess growth hormone that results in the overgrowth of some bones. Gigantism is the term used when too much growth hormone is present before all normal bone growth has stopped (childhood), and acromegaly is the term used when too much growth hormone is released after normal bone growth has stopped.
  
  
• Shock.
  
  
• Complications of diabetes.
  
  
• Toxemia during pregnancy. In pregnant women, abnormal levels could indicate high blood pressure (preeclampsia).
  
  
• Hypoparathyroidism. A condition in which an individual produces too little of  parathyroid hormone causing abnormal calcium and phosphorus levels.
  
  
• Excessive exercise.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor or healthcare professional the following questions related to the waste product test:

1. Is a waste product test required for my condition?
   
   
2. Do I need to make any special preparations for the test?
   
   
3. Am I taking any medications that might affect test results?
   
   
4. Where can I have the test performed?
   
   
5. When and from whom will I learn my results?
   
   
6. What are the normal levels for my gender, age and health?
   
   
7. What levels will indicate a significant problem?
   
   
8. What do you suspect is the cause for the abnormal levels?
   
   
9. Is there someone I can ask questions once I have received the results?
   
   
10. How often will I need to have these tests?
    
    
11. Will I need any additional diagnostic tests?
    
    
12. Can I take this test if I am pregnant?