Why do we have to fast for some blood tests?
If you are planning to take a blood test anytime soon, then do make sure you are ready. Sometimes before giving your blood sample, you need to fast which means you can’t eat or drink (except water) for a few hours before the test. It is because after the food gets digested, our blood absorbs all the nutrients from the food to spread them across the body. Due to this presence of fresh nutrients in the blood, some blood test results may alter. And naturally, an altered result will lead to a wrong diagnosis. Which means, getting treated for a problem that you actually never had while the original problem remains untreated. Here is a list of blood tests that require fasting.
- Blood Glucose or Sugar Test
To diagnose and to keep a tab on diabetes, the glucose or sugar levels in your blood are monitored through this test. You are not supposed to eat or drink (except water) for at least eight to ten hours before the test. Otherwise, your test result will reveal a very high sugar level, when in reality it might not be that elevated. This happens because once the food is digested; the amount of glucose in the blood remains high for quite a while.
2. Iron Blood Test
Anaemia and iron deficiency is detected through this test. A minimum of eight hours fast is needed prior to the test and is usually conducted in the morning. Our body tends to absorb iron fast; hence iron supplements are not to be taken twenty four hours before the test.
- Lipid Profile
This blood test shows the levels of the following in the blood stream –
- Total cholesterol,
- Good cholesterol (HDL),
- Bad cholesterol (LDL) and
- Triglycerides (fatty substances)
Nine to twelve hours fast is advised before the test as food drastically shoots up the levels of bad cholesterol (LDL). Alcohol too should not be consumed a full twenty four hours prior to the test as it affects the levels of triglycerides.
- Vitamin B 12 Blood Test
It is prescribed not to eat or drink (except water) for at least ten hours before the test. Lack of vitamin B 12 leads to a type anaemia and harms the nervous system. Therefore keeping a track of its quantity is a must.
Similarly, you will need to fast before undergoing folate deficiency blood test, C-Peptide test, etc. Chewing gum should also be avoided as it contains sugar but the good news is that you are allowed to consume as much water you want during these fasts. Regarding the consumption of regular medicines prior these tests, do consult your doctor. When you book a test with Apollo Diagnostics please call our customer care at 040 44442424 to know about the tests’ dos and don’ts and if fasting is required.