How long before a blood test should I stop exercising?

How Long to Stop Exercising Before a Blood Test

You should not exercise for at least 24 hours before a blood test to ensure accurate results. 1

Exercise Effects on Blood Test Parameters

• Exercise can significantly alter various blood parameters that may affect the interpretation of test results 1:
  • Strenuous physical activity can cause a 25% increase in PSA levels after cycling and a 12% increase after treadmill exercise 2
  • Exercise can elevate serum erythropoietin concentrations, particularly if performed after blood withdrawal 3
  • Physical activity alters cardiac output, blood pressure, and peripheral blood flow distribution 1

Specific Guidelines for Pre-Test Preparation

• Avoid eating for 3 hours before the blood test 1
• Do not smoke for at least 8 hours before testing 1
• Avoid unusual physical efforts for at least 12 hours before testing 1
• For more accurate results, avoid strenuous exercise completely for 24-48 hours before the test 1
• For specific tests like PSA measurement, men should abstain from cycling for several days and at least 24 hours before the test 2

Why Exercise Affects Blood Test Results

• Exercise causes physiological changes that can impact test results 1:
  • Increases in heart rate and blood pressure 4
  • Shifts in fluid balance and blood volume 1
  • Changes in oxygen uptake and carbon dioxide output 5
  • Alterations in hormone levels (including growth hormone) 3
  • Increased blood lactate levels 3

Special Considerations

• For diagnostic exercise testing itself, patients should:
  • Wear comfortable clothing and appropriate footwear 1
  • Take routine medications with small amounts of water 1
  • Be aware that some medications (especially β-blockers) may need to be held if the test is for diagnosing ischemia 1

Common Pitfalls to Avoid

• Exercising too close to blood test time can lead to:

  • Falsely elevated enzyme levels 1
  • Misinterpretation of cardiac markers 1
  • Inaccurate PSA measurements that could lead to unnecessary follow-up testing 2
  • Altered hormone levels that don't reflect baseline status 3

• For PSA testing specifically, cycling has a particularly strong effect that can persist for up to 48 hours (and sometimes longer in individual cases) 2