Whether your child needs to fast before a blood test depends entirely on what is being tested. Cholesterol (lipid panel) and fasting glucose tests require 8–12 hours of fasting. Most other common pediatric lab tests — including CBC, thyroid tests, iron studies, and lead levels — do not require fasting. Water is always allowed regardless of fasting requirements. If you are unsure whether your child’s specific test requires fasting, call Spring Valley Pediatrics at 202-966-5000 before the appointment.
You’re probably used to getting blood drawn at your yearly check up with your doctor. We use these tests to glean all kinds of information about our patients. Depending on the age of the patient we may check for anemia (not enough red blood cells), lead level, Vitamin D, and cholesterol. For routine blood tests, our patients can have them done anytime regardless of if they have recently eaten. However, sometimes we ask that our patients have fasting labs done. How do you do them and why are they done?
Fasting labs mean that you don’t eat or drink anything besides water for 8-12 hours before coming in for your blood draw. You can have dinner the night before but nothing to eat in the morning before coming to the office. You can, and should, take any medications you would normally take in the morning.
Be sure to drink water – lots and lots of water! When you are dehydrated (don’t have enough water in your body) your veins are smaller which makes it harder to draw your blood. You also may feel light-headed if you have not had enough water to drink. Feel free to bring a snack with you to enjoy once your blood is drawn.
Fasting labs give us a more accurate look at your cholesterol, triglycerides and glucose (blood sugar). When you eat or drink, nutrients and ingredients enter your blood stream and can falsely elevate these tests. A fasting test gives your doctor more accurate information about your body.
If you are not sure if you should fast before your labs, call our office to ask.
Frequently Asked Questions About FASTING LABS
Does my child need to fast before a blood test?
It depends on the test. Fasting IS required for: lipid panels (cholesterol), fasting glucose, and certain metabolic panels. Fasting is NOT required for: complete blood count (CBC), thyroid tests (TSH, T4), iron studies, lead levels, vitamin D, and most allergy tests. When in doubt, call our office — we will tell you exactly what is required.
How long does a child need to fast before labs?
When fasting is required, children typically fast for 8–12 hours. This means no food and no drinks other than water. Scheduling the appointment for early morning — after an overnight fast — is usually the easiest approach.
Can my child drink water while fasting?
Yes — water is always permitted during a fasting period. Staying hydrated makes the blood draw easier. Clear water only — no juice, milk, sports drinks, or flavored water.
What happens if my child accidentally eats before fasting labs?
Call our office. Depending on the test, we may be able to reschedule later that day after a shorter wait, or reschedule the appointment entirely. For a lipid panel or fasting glucose, eating before the test will affect results and the test will need to be repeated.
Can infants and toddlers fast before blood tests?
Young infants should generally not fast for long periods. For infants under 6 months, we typically schedule the draw 2–3 hours after a feeding. For toddlers, we try to schedule early morning appointments to minimize fasting time. Always ask our team for specific guidance for your child’s age.
What should I do if my young child cannot tolerate fasting?
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