Understanding Your Lab Work

A guide to your lab work

If you’ve been diagnosed with chronic kidney disease (CKD), thorough testing can help you and your healthcare team understand what is going on inside your body and whether your treatment plan is working as well as it should.

Your doctor will perform different tests based on which stage of kidney disease you’re in. People in the earlier stages of kidney disease undergo tests that measure their kidney function. People in the later stages of kidney disease and people on dialysis are tested to see if their treatments are effective. If you’re a DaVita® patient, you can see your lab results on the DaVita Health Portal™ and share them with your kidney care team. Below is an overview of some of the most common tests your doctor may order for you.

Serum creatinine

  • Purpose: To determine how much creatinine is in the bloodstream.
  • Normal range: .8 to 1.4 milligrams per deciliter (mg/dl).
  • How this test is conducted: A blood sample is taken and sent for analysis.
  • Test date: Throughout the early and laterstages of CKD, including end stage renal disease (ESRD).

GFR—Glomerular filtration rate

  • Purpose: To determine how much kidney function a person has.
  • Normal range: 90+, with little or no protein or albumin in urine.
  • How the test is conducted: This test is a calculation based on your creatinine level, age, race, gender and other factors.
  • Test date: Throughout every stages of CKD, including ESRD.

Changes to your GFR will tell your doctor how fast or slow your condition is progressing.

Stage

GFR Level and Description

Stage 1

>90 mL/min; normal or high GFR

Stage 2

60 to 89 mL/min; mild decrease in GFR

Stage 3A

45 to 59 mL/min; moderate decrease in GFR

Stage 3B

30 to 44 mL/min; moderate decrease in GFR

Stage 4

15 to 29 mL/min; severe decrease in GFR

Stage 5

Less than 15 mL/min or on dialysis; kidney failure

Microalbumin

  • Purpose: To detect a protein called albumin in the urine, which may indicate kidney damage.
  • Normal range: Almost no albumin should be detected.
  • How this test is conducted: A urine sample is taken from the person being tested.      
  • Test date: In the early diagnostic stage of CKD. Yearly for people with diabetes or hypertension.


BUN — Blood urea nitrogen

  • Purpose: To detect elevated waste levels in the bloodstream, which is an early sign of reduced kidney function.
  • Normal range: 7 to 20 milligrams per deciliter (mg/dl).
  • How this test is conducted: A blood sample is taken and sent for analysis.
  • Test date: In the diagnostic stage, the early and later stages of CKD, including ESRD, to measure effectiveness of treatment.

CCr — Creatinine clearance

  • Purpose: To determine how well the kidneys are filtering creatinine and getting rid of waste.
  • Normal range: For men, normal values can range from 97 to 137 milliliters per minute. For women, normal values can range from 88 to 128 milliliters per minute.
  • How this test is conducted: Blood and urine samples are taken and sent for analysis.
  • Test date: When a person is starting dialysis or to assist with a nutritional assessment.

Hb — Hemoglobin

  • Purpose: To determine the amount of hemoglobin in red blood cells and screen for anemia.
  • Normal range: In an adult, 12 to 18 grams per deciliter of blood.
  • How the test is conducted: A blood sample is taken and sent for analysis. This test is often part of a comprehensive test called a complete blood count (CBC) or complete blood test.
  • Test date: Throughout the early and later stages of CKD, including ESRD.

Hct — Hematocrit

  • Purpose: To determine the percentage of red blood cells in the blood and screen for anemia.
  • Normal range: For adult females the range is usually 36to 47 percent, for adult males the range is 40  to 53 percent. For dialysis patients the recommended target hematocrit range is 33 to 36 percent.  
  • How this test is conducted: A blood sample is taken and sent for analysis. This test is often part of a comprehensive test called a CBC or complete blood test.
  • Test date: Throughout the early and later stages of CKD, including ESRD.

URR — Urea reduction ratio

  • Purpose: To measure how much urea was removed during a hemodialysis session.
  • Target range: URR should be more than 65 percent.
  • How this test is performed: A blood sample is taken at the start of a dialysis session and another sample is taken afterwards.
  • Test date: Once every 12 to 14 dialysis sessions, this is approximately once a month.

Kt/V

Kt/V is a mathematical formula, where:

“K” = clearance (the amount of urea your dialyzer has removed (liters/minute)) multiplied by

“t” = time (the duration of treatment (minutes)) divided by

“V” = volume (the amount of body fluid (liters)).

  • Purpose: To determine how well dialysis  is cleaning your blood.
  • Target range for hemodialysis patients: More than 1.2.
  • Target range for peritoneal dialysis patients: More than 2.0.
  • How this test is conducted: For hemodialysis, a blood sample is taken at the start and end of a dialysis session. Information about your treatment is collected, and a computer calculates the Kt/V result. For peritoneal dialysis (PD), a blood sample is taken along with a sample of the PD fluid and the volume removed over 24 hours.
  • When this test is performed: Once a month for hemodialysis patients and once every four months for PD patients or after a prescription change.

A1c — Glycosylated hemoglobin test, also known as hemoglobin A1c

  • Purpose: To determine average blood glucose levels over a two to three month period. This test is for people with diabetes.
  • Target range: American Diabetes Association goal is less than 7.0 gm/dl for good blood glucose management for diabetics.
  • How this test is conducted: A blood sample is taken and sent for analysis.
  • Test date: This test is done when you are first diagnosed with diabetes and then two to four times a year thereafter.

Blood electrolyte levels

  • Purpose: To measure the levels of electrolytes (sodium, potassium, calcium, phosphorus) in the body that help move nutrients and waste in and out of cells.
  • Normal range: Sodium: 135 to 145 mEq/L. Potassium: 3.5 to 5.0 mEq/L. Calcium: 8.5 to 10.5 mg/dL. Phosphorus: 3.0 to 4.5 mg/dL. The goals for people on dialysis vary from some of these levels—potassium goal 3.5 to 5.5, calcium 8.4 to 9.5, phosphorus 3.5 to 5.5.
  • How the test is conducted: A blood sample is taken and sent for analysis.
  • Test date: During stages 3, 4 and 5 of kidney disease, when the renal diet is prescribed or if the person is on dialysis.

Know your labs

Your dietitian, doctor and other healthcare team members will monitor your test results and recommend dietary adjustments or make changes to your treatment. If you don’t know what your numbers are, or have questions about these tests, ask a member of your kidney care team for more information. Also get your lab results on the DaVita Health Portal™ when you’re a DaVita patient.

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