It was the morning of my blood test and the doctor had strictly instructed me to come empty stomach. I felt my head was splitting without my morning cup of tea and stomach rumbling with the last morsel of food consumed before 9 pm the previous night. I was tempted to have a drink.
If you feel the same, don't give into temptations. Remember, your Doctor is taking any revenge from you, but some of the blood tests should be carried out in fasting else they give wrong results. So it's for your own good!
Most blood tests like pregnancy blood test, or kidney, liver function test do not require fasting as the food will not have bearing on the results.
So what is this all about, let's see:
Why do I have to fast?
Blood tests are prescribed to monitor health and nutritional status of the body and assess the risk to certain diseases like diabetes, high cholesterol leading to heart ailments. Most components of the blood don't get affected within a short span of time by consuming nutrients, but certain substances like glucose, iron, and lipids remain elevated several hours after eating or drinking. Fasting for a period of 10-12 hours (generally overnight), decreases the variability in the levels of these substances in the blood. This ensures the test results are not influenced by the food and can be interpreted correctly by the doctor. If you don't fast and eat or drink before the fasting blood glucose test can shoot up the blood sugar levels even if you did not have any ailment. This will lead to wrong diagnosis and unnecessary medications and complications. Remember, doctors, use the fasting test results as baseline results. This result is compared with tests over a period to determine the actual levels.
How do I fast?
While fasting, you should not eat or drink anything for a period of minimum 8 hours or as prescribed by the doctor. This also means no breakfast in the morning or tea or coffee or milk but regular medications are permitted. Drinking water before the blood test is allowed and recommended as it will make the veins full and easy to locate them to draw blood.
What if I fail?
In case you fail to fast for the prescribed number of hours, it is better to let the doctors know what and when you have had so that they can interpret the results accordingly.
When can I start eating?
You can start eating once the tests are done. In fact, most hospitals themselves provide light breakfast
Which test requires fasting?
- Glucose tolerance test
- Pregnancy glucose tolerance test
Along with food, the doctor may even ask to avoid alcohol certain medications, nutritional supplements before the test. However, one should intake their prescribed dose of medications and supplements even during fasting.