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Glomerular filtration rate (GFR) is a test used to check how well the kidneys are working. Specifically, it estimates how much blood passes through the tiny filters in the kidneys, called glomeruli, each minute.
See also:
Alternative NamesGFR; Estimated GFR; eGFR
How the test is performedBlood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
The blood sample is sent to a lab, where the creatinine level is tested. The lab specialist uses combines your creatinine level with several other factors to estimate your glomerular filtration rate (GFR). Different formulas are used for adults and children. The formula will include some or all of the following:
- Age
- Creatinine measurement
- Gender
- Height
- Race
- Weight
Certain drugs can interfere with test results. Tell your doctor about all medicines you are taking, including over-the-counter ones.
How the test will feelWhen the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there might be some throbbing.
Why the test is performedThe GFR test measures how well your kidneys are filtering a waste called creatinine, which is produced by the muscles. When the kidneys aren't working as well as they should, creatinine builds up in the blood.
Your doctor may order this test if there are signs that your kidneys are not working properly. It may also be done to see how far kidney disease has progressed.
The test is recommended for people with chronic kidney disease and those at risk for it due to:
- Diabetes
- Family history of kidney disease
- Frequent urinary tract infections
- Heart disease
- High blood pressure
- Urinary blockage
According to the National Kidney Foundation, normal results range from 90 - 120 mL/min. Older people will have lower normal GFR levels, because GFR decreases with age.
Normal value ranges can vary slightly among different laboratories. Talk to your doctor about what your specific test results mean.
What abnormal results meanLevels below 60 mL/min for 3 or more months are a sign of chronic kidney disease. Those with GFR results below 15 mL/min are a sign of kidney failure.
What the risks areVeins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but can include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
The creatinine clearance test, which involves a 24-hour urine collection, can also provide an estimate of kidney function. However, this method is not always accurate.
GFR can increase during pregnancy.
ReferencesK/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Kidney Disease Outcome Quality Initiative. Am J Kidney Dis. 2002;39(2 Suppl 1):S1-246.
Johnson CA, Levey AS, Coresh J, Levin A, Lau J, Eknoyan G. Clinical practice guidelines for chronic kidney disease in adults: Part II. Glomerular filtration rate, proteinuria, and other markers. Am Fam Physician. 2004;70:1091-1097.
Snyder S, Pendergraph B. Detection and evaluation of chronic kidney disease. Am Fam Physician. 2005;72:1723-1732, 1733-1734.
What else can I help you with?
Capsular hydrostatic pressure?
Capsular hydrostatic pressure refers to the fluid pressure within the glomerular capsule of the kidney. It is involved in the process of filtration of blood to form urine, along with blood pressure and oncotic pressure. An increase in capsular hydrostatic pressure can affect the rate of urine formation.
How does pressure affect filtration?
Increased pressure can help to overcome resistance in the filtration process, allowing for faster flow rates and more efficient separation of solids from liquids. Higher pressure can also lead to reduced filter cake formation and improved particle retention. However, excessive pressure can damage the filter media and reduce the overall effectiveness of the filtration process.
How much energy does it use to filter water?
The energy required to filter water depends on the type and size of the filtration system used. It can vary from a few watts for small household filters to several kilowatts for larger industrial filtration systems. Factors such as flow rate, pressure, and filter type all influence the energy consumption of water filtration.
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To select the size of a gravity disc for a purifier, first consider the flow rate of water that needs to be filtered. Then, choose a gravity disc size that is suitable for that flow rate to ensure effective filtration. Additionally, consider the specific requirements of your purifier system and choose a gravity disc size that aligns with those specifications for optimal performance.
What are the key features to consider when designing a swimming pool weir?
When designing a swimming pool weir, key features to consider include the size and shape of the weir, the flow rate of water, the type of filtration system, and the overall aesthetics of the pool. It is important to ensure that the weir is properly sized to handle the water flow and debris, and that it complements the design of the pool.
How does glomerular hydrostatic pressure effect filtration rate?
Glomerular hydrostatic pressure is the primary driving force for filtration rate in the kidneys. An increase in glomerular hydrostatic pressure will increase the rate of filtration by pushing more fluid and solutes out of the blood and into the renal tubules. Conversely, a decrease in glomerular hydrostatic pressure will decrease the filtration rate.
Is the kidney functional when the glomerular filtration rate is zero?
no
What is injected to measure glomerular filtration rate?
inulin
What does the medical abbreviation GFR mean?
Glomerular Filtration RateThe GFR stands for glomerular filtration rate, and assesses kidney function.
What does the medical abbreivation GRF mean'?
Glomerular filtration rate
What is the normal adult glomerular filtration rate?
Glomerular filtration rate is the rate at which fluid is filtered by the kidneys. The normal rate for humans is 125mL/min or 180L/day. The fluid that is filtered (and not reabsorbed later) is excreted as urine.
Does dilation of the afferent arteriole decrease Glomular filtration rate?
No, dilation of the afferent arteriole typically increases glomerular filtration rate by allowing more blood flow into the glomerulus. Constriction of the afferent arteriole would decrease the glomerular filtration rate.
Filtration at the glomerulus is directly related what.?
Filtration at the glomerulus is directly related to the hydrostatic pressure in the glomerular capillaries, the oncotic pressure in the Bowman's capsule, and the glomerular filtration rate (GFR). These factors influence the movement of fluid and solutes across the glomerular filtration barrier.
What is the effect of constricted arterioles in the glomerular filtration rate?
Constricted arterioles in the glomerulus can lead to a decrease in the glomerular filtration rate (GFR) by reducing the amount of blood flow entering the glomerulus. This can result in decreased filtration of waste and reduced urine production.
Define glomerular filtration rate Name and describe the pressures which are effective at the glomerulus under normal conditions and result in glomerular filtration?
Glomerular filtration is a passive process in which hydrostatic pressure forces fluids and solutes through a membraneThe glomerular filtration rate (GFR) is directly proportional to the net filtration pressure and is about 125 ml/min (180 L/day).The glomeruli function as filters. High glomerular blood pressure (55 mm Hg) occurs because the glomeruli are fed and drained by arterioles, and the afferent arterioles are larger in diameter than the efferent arterioles.
Macula densa feedback (tubuloglomerular feedback) decrease or increase?
The macula densa is involved in tubuloglomerular feedback to help regulate glomerular filtration rate. An increase in NaCl concentration at the macula densa leads to vasoconstriction of the afferent arteriole, decreasing glomerular filtration rate. Conversely, a decrease in NaCl concentration leads to vasodilation of the afferent arteriole, increasing glomerular filtration rate.
Where can one find the glomerular filtration rate?
Glomerular filtration rate (GFR) is a measurement of how well one's kidneys are functioning. It is typically estimated on the basis of serum creatinine levels. One can learn their estimated GFR by visiting their physician.
