How to Prepare for a Lab Test
Proper preparation for lab tests is essential for accurate results, and following your provider's specific instructions is the best way to ensure reliable data.
How do I prepare for a lab test?
Lab tests analyze blood, urine, or tissue to help diagnose, screen for, or monitor diseases. To ensure your results are accurate, you must:
- Follow all instructions provided by your health care professional.
- Be honest if you did not follow instructions exactly, as even minor deviations can affect results.
- Inform your provider about all medications, vitamins, and supplements you are taking.
Common preparation steps
The most common requirement is fasting, which means not eating or drinking anything except water for a specified period (often overnight). This prevents nutrients from food from interfering with your blood chemistry. Other preparations may include:
- Avoiding specific foods, drinks (like alcohol or herbal tea), or smoking.
- Avoiding strenuous exercise or sexual activity.
- Adjusting medication schedules only if directed by your provider.
- Drinking extra water to keep veins hydrated for blood draws.
Tests requiring special preparation
Some tests have unique requirements:
- Fasting tests: Blood glucose, cholesterol, triglycerides, and calcitonin tests.
- Dietary/Activity restrictions: Creatinine (avoiding cooked meats), 5-HIAA (avoiding foods like avocados, bananas, and walnuts), and Pap smears (avoiding douching, tampons, or sex for 24–48 hours).
- Rest: Cortisol tests may require resting before the sample is taken.
Always clarify your preparation instructions with your provider before the day of your test to ensure you understand exactly what is required.