Should I stop taking my prescribed medications on the day of a blood test?

Should You Stop Medications on the Day of a Blood Test?

For routine blood tests, continue taking all your prescribed medications as usual on the day of testing—there is no general need to stop medications for standard laboratory work. 1

General Principle for Routine Blood Work

• Take medications normally with small amounts of water before routine blood tests 1
• The only universal requirement is fasting from food for the specified time period (typically 3 hours for routine tests, 8 hours for lipid panels or glucose testing) 1
• Medications themselves do not need to be stopped unless specifically instructed by your ordering physician 1

Specific Exceptions Where Medication Timing Matters

When Testing is for Ischemia Detection (Exercise Stress Tests)

• Beta-blockers and other anti-ischemic drugs may be held 24+ hours before testing if the purpose is to diagnose coronary artery disease, as these medications can mask ischemic changes and reduce test sensitivity 1
• However, if the test is to assess functional capacity or medication effectiveness, continue all medications 1
• This decision requires involvement of your referring physician—never stop cardiac medications without explicit instruction 1

Sick Day Situations (Not Routine Blood Tests)

• Temporarily stop specific medications during acute illness that increases risk of kidney injury, including: RAAS blockers (ACE inhibitors, ARBs), diuretics, NSAIDs, metformin, and SGLT2 inhibitors 1
• This applies when you have serious intercurrent illness (vomiting, diarrhea, fever) with GFR <60 mL/min/1.73 m², not for routine blood draws 1

Common Pitfalls to Avoid

• Do not confuse fasting requirements with medication instructions: Fasting means no food, but medications can still be taken with water 1
• Do not stop medications on your own initiative: If medication adjustment is needed for testing purposes, your physician will provide specific tapering instructions 1
• Bring a complete medication list including doses and timing to your blood test appointment, as this information is essential for result interpretation 1

When to Contact Your Physician

• If you're on beta-blockers and having an exercise stress test—clarify whether to continue or hold 1
• If you're acutely ill and on medications like metformin, diuretics, or ACE inhibitors—discuss temporary discontinuation 1
• If you're uncertain about any specific medication instructions for your particular test 1

The key distinction: Routine blood tests (chemistry panels, complete blood counts, metabolic panels) do not require stopping medications. Only specialized testing for specific diagnostic purposes (like unmedicated exercise stress tests) or acute illness situations warrant medication adjustments, and these require physician guidance.