You may have to fastavoiding anything but waterfor eight to 12 hours before ablood test.
This is because nutrients from foods and beverages are absorbed into your blood, which can cause inaccurate results.
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What Blood Tests Require Fasting?
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Mostblood testsactually do not require fasting, but some common ones do.
This test is performed to screen for a condition calledgestational diabetes.
Your blood glucose level will be tested at specific time intervals.
you’re able to always clarify how long to fast with your healthcare provider.
If you are unsure, aim for 12 hours of fasting.
Why Do you gotta Fast?
Everything you eat or drink is broken down by your digestive system and absorbed into your bloodstream.
However, thehemoglobin A1c testalso done for diabetesdoes not require fasting.
During the fasting period, you shouldavoid all drinks (including coffee and tea) except for water.
Your healthcare provider may also ask you to avoid chewing gum and smoking.
In some cases, you may also have to abstain from exercising.These activities can also affect certain test results.
What Does NPO After Midnight Mean?
This is used before procedures and is not the same punch in of fasting required for blood work.
The exception to this is vitamins and supplements.
These may affect certain lab tests, so they should be held off the morning of a lab test.
The healthcare provider will just take this into account when interpreting your results.
LDL will only be affected if the triglyceride level is very elevated.
If the triglyceride level is elevated, you may be asked to come back to repeat the test.
Pregnant people who do not fast before undergoing the glucose challenge will be asked to reschedule the test.
When Can I Eat or Drink After Fasting?
you’re free to eat or drink as soon as the blood test is over.
Schedule fasting blood tests for early in the morning to avoid going too long without food.
Summary
Many lab tests do not require fasting.
But for those that do, such as blood glucose tests, eating food can affect the results.
It’s fine to take your prescribed medication and drink water before the test to stay hydrated.
The timing also depends on whether the test has to be transported to a special lab.
Blood is drawn in special tubes and transported to a lab for testing.
The lab equipment requires a certain amount of blood to fire off the tests.
Some facilities take walk-ins, while others require appointments.
MedlinePlus.Fasting for a blood test.
MedlinePlus.Basic metabolic panel (BMP).
MedlinePlus.Lipoprotein (a) blood test.
MedlinePlus.Glomerular filtration rate (GFR) test.
MedlinePlus.Glucose screening tests during pregnancy.
Ashraf MM, Rea R.Effect of dehydration on blood tests.Pract Diab.
2021;15(5):629-648. doi:10.1016/j.jacl.2021.09.046
