You booked your lab appointment. Now comes one of the most common questions:
Do I need to fast?
The answer depends on the tests you are having.
Some blood tests require little or no special preparation. Others may be affected by food, beverages, exercise, medications or supplements.
Following the correct instructions matters because preparation can influence certain laboratory measurements.
If you are scheduled for local lab work at Avendano Health, appointments are now available Monday through Friday from 8 AM to 12 PM.
Here is how to arrive prepared.
Still need to select your tests?
If you still need to select your testing, browse General Lab Work for individual tests or compare Wellness Bundles for broader testing packages before scheduling your appointment.
Do You Need to Fast Before a Blood Test?
Not necessarily.
For example, a CBC usually does not require special preparation when performed by itself.
If other tests are being collected at the same time, however, you may receive fasting instructions.
A comprehensive metabolic panel may require fasting for several hours depending on how the test was ordered and what other testing is being performed.
The most important rule is simple: Follow the instructions provided for your specific tests rather than assuming every blood test requires fasting.
If you are told to fast, MedlinePlus notes that fasting commonly means consuming nothing except plain water for a specified number of hours, often approximately 8–12 hours depending on the test.
Can You Drink Water While Fasting?
Usually, plain water is allowed when you have been instructed to fast for a blood test.
In fact, staying hydrated can make blood collection easier because adequate hydration helps maintain fluid in your veins.
Coffee, juice, soda and other beverages are not substitutes for plain water during a laboratory fast unless your healthcare provider specifically tells you otherwise.
What About Medications and Supplements?
Do not stop prescription medication simply because you are fasting.
Some medications and supplements can affect certain laboratory measurements, but stopping medication without medical guidance can also be unsafe.
Tell your healthcare provider or laboratory team about prescription medications, over-the-counter products, vitamins and supplements you take, and follow the instructions given for your particular tests.
What Should You Bring to Your Appointment?
Bring any information or materials specifically required for your testing.
If you are coming for routine direct-access testing, know which tests or bundle you selected and follow the preparation instructions associated with them.
If another provider has requested specific laboratory work, bring the applicable order or testing information when required.
And if you are coming for a Rupa Health or other supported specialty laboratory kit, bring the kit with you.
Our specialty collection service handles collection, centrifugation when required, temperature holding and shipping preparation for supported kits. Specialty draws require advance scheduling.
If another provider has given you a specialty testing kit, your appointment follows a different pathway. Review Avendano Health's Specialty Draws service before arriving so you know what to bring and how your collection will be handled.
Patients with Rupa Health or another supported specialty kit should use the Specialist Draws appointment pathway rather than booking ordinary general lab work.
Have a specialty kit instead of regular lab work?
Go directly to our Rupa Health & Specialty Draw service to review the $50 collection-and-processing pathway and schedule the appropriate appointment.
What If You Accidentally Break Your Fast?
Tell the laboratory team.
Do not hide the fact that you ate, drank something besides water, exercised, or took something that may affect the test.
Depending on the test, it may still be possible to proceed, or rescheduling may provide a more useful result.
Accurate information is more valuable than trying to force a test into the original appointment.
Schedule Morning Lab Work in Boca Raton
Morning appointments can be convenient when fasting is required because much of the fasting period occurs overnight.
Our Boca Raton Local Lab is now available Monday through Friday from 8 AM to 12 PM by appointment, making morning scheduling especially practical for patients who have fasting instructions.
For standard blood work, review General Lab Work.
For broader preventive testing, review Wellness Bundles.
For Rupa Health and supported specialty kits, use Specialty Draws.
Choose your lab appointment
Need individual blood tests? View General Lab Work →
Want a bundled wellness panel? Compare Wellness Bundles →
Already have a specialty testing kit? Schedule a Specialty Draw →
Frequently Asked Questions
How long do I need to fast?
When fasting is required, the length depends on the test. MedlinePlus notes that fasting is commonly around 8–12 hours, but you should follow the instructions for your specific test.
Can I drink water?
Plain water is generally allowed during a laboratory fast unless you were given different instructions.
Can I take my medication?
Do not stop medication on your own. Ask the healthcare professional who ordered or manages your testing if medication timing needs to change.
Does a CBC require fasting?
A CBC alone usually does not require special preparation, although fasting may be necessary if other tests are collected at the same time.