Creatinine is produced when a substance known as creatine breaks down in the body. Creatine is produced regularly by the body and is used to help procure energy for the muscle cells to contract. The vast majority of creatinine is excreted by the kidneys.

When is the test used?

The test is primarily used to check the functioning of the kidneys; in most cases, a blend of blood and urine tests are carried out to produce a ’creatinine clearance’ test, which assesses how effectively the kidneys are sifting molecules out of the bloodstream.

The test is usually ordered when a doctor suspects a patient is suffering from kidney problems, but it can also be used as a routine test for a patient who has a range of symptoms which could be attributed to several different types of illness.

The test may also be used on patients who are being treated for kidney disease to see if the treatment is working well.

How is the test performed?

The test is done by collecting a sample of blood; the sample is usually taken from a vein in the arm using a needle; the needle is inserted into the vein and the blood is drawn and collected in a syringe. Once the sample has been collected, it can be bottled and sealed before being labelled and sent away to the laboratory for analysis.

What do the test results show?

Increased levels of creatinine in the blood may indicate that the kidneys are not functioning as well as they should be; this could be down to several different illnesses, including:

  • Urinary tract obstruction
  • Pyelonephritis (this is an infection of the kidneys)
  • Glomerulonephritis (this is when the blood vessels in the kidneys become swollen)
  • Acute tubular necrosis (this is when the cells in the tiny blood vessels in the kidney die)
  • Decreased blood flow to the kidneys (this may be caused by dehydration, shock, diabetes or heart failure)

Creatinine levels may also increase after a muscle injury.

Women generally have lower levels of creatinine because they have less muscle mass. Eating a lot of red meat may temporarily increase levels of creatinine and taking supplements can also increase levels (some body builders take creatinine supplements).

Specific Blood Tests

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