For most of the blood tests, no special preparation is necessary. Our body closely monitors blood chemistry values and maintains them within normal ranges, despite what we eat and drink. However, there are a few tests that do require special preparation to provide standardized results.
For example, both cholesterol and blood sugar are significantly affected by food. In fact, studies have shown that high fat food choices may affect cholesterol levels for an entire week. Therefore, we should try to eat our usual foods in the week prior to blood work. Out of the ordinary choices such as pizza or fatty foods may skew the results.
After eating, the body converts extra calories to storage forms (triglycerides) which move through the blood to fat tissue. As a result, transient increases in blood triglyceride levels may occur. To compensate for this, fasting for at least 12 hours is recommended prior to the lipid/cholesterol test. In the fasting state, our lipids should be at their baseline.
Similarly, blood sugar is very sensitive to food and drink. Fruit juices and concentrated sweets (cookies, candy, desserts) may significantly raise blood sugar levels. By measuring sugar values in the fasting state, these variables can be eliminated.
Following a 12 or more hour fast, there may be some dehydration which makes finding the blood vessel for the draw more difficult and it may skew the results of the kidney function tests. Therefore, it is always wise to drink some water prior to the blood work to rehydrate and return blood volume to normal.
Other tests that may require special consideration include blood levels for testosterone or B12 supplementation and anti-seizure medications. It is important to insure that these medications remain adequate, throughout the month. Therefore, it is best to test these levels at their lowest point, just prior to the next injection.
Healthy Habits before Blood Tests:
- For the most accurate reflection of your blood chemistries and cholesterol, eat your usual diet in the weeks immediately prior to the tests. If you have been on vacation or eating out an unusual amount, wait until you have re-established your general diet before getting the blood work done.
- Fast for at least 12 hours prior to cholesterol or blood sugar testing. Be sure to drink some water, however, to maintain adequate hydration.
- If you are testing blood levels of a medication or supplement, make sure that you have been taking it regularly in the month prior to the test.