If your doctor orders routine blood work, it might include a lipid panel and fasting glucose test to monitor your cholesterol and blood sugar levels. Such tests performed periodically are part of a standard health maintenance protocol when you're over 20 years old. Because eating affects the cholesterol and sugar levels in your blood, fasting properly is necessary when you're scheduled for routine lab work. Otherwise your lab work results will be inaccurate.
Step 1
Call the lab. Don’t rely on the hospital or clinic to contact you prior to your lab appointment with instructions. Phone two or three days before your appointment -- or sooner -- and confirm exactly which tests you need to prepare to take. Certain types of blood tests do not require fasting.
Step 2
Set your deadline to determine what time you should begin fasting. If, for instance, your lab appointment is scheduled for 8:30 a.m., you shouldn’t eat anything after 8:30 p.m. the previous evening. Up until that point, eat as you normally would. If you typically enjoy a bedtime snack, skip it the evening before your fasting blood test or eat it earlier.
Step 3
Stop eating 12 hours before your scheduled appointment. Do not ingest any type of food or beverage -- except water -- once you begin fasting. If you smoke, set the cigarettes aside until after your test. Even chewing sugarless gum can affect the accuracy of fasting blood test results. Relax and sip water, but refrain from putting anything else into your mouth.
Step 4
Skip the morning coffee. Some labs tell patients it’s OK to enjoy a cup of black coffee before a blood draw, but your results will be more accurate if you don’t. Your body absorbs caffeine rapidly, and because coffee beans contain a high percentage of polysaccharides -- a type of sugar -- a single cup temporarily raises your blood glucose level.
Step 5
Drink eight to 10 glasses of water the day before your appointment, and a glass before you arrive at the lab. When you’re hydrated, your veins are plumper and easier for the phlebotomist to locate.
Tips and Warnings
- In most cases, your doctor will advise you to take your usual prescription medications during your fasting period. Once the phlebotomist draws your blood, you’re free to eat and drink what you’d like. The lab might offer you a small snack or can of juice after your appointment to ensure that your blood sugar level doesn’t drop too drastically.
- If your blood work includes a lipid panel, the laboratory professionals at Lab Tests Online warn against consuming alcoholic beverages 24 hours before your lab appointment; alcohol might prevent an accurate reading of triglycerides in your blood. Blood thinning medications increase the risk of excessive bleeding. California Pacific Medical Center advises informing the lab if you’re taking blood thinners; the phlebotomist can then take extra precautions to stop the bleeding after your blood draw. If you’ve recently suffered a heart attack, had surgery, given birth or been treated for an infection, your doctor might recommend waiting two months or more before taking a cholesterol test.
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