What Is It Used For
If you take prescription thyroid hormone medicine because of hypothyroidism or because you had your thyroid removed, youll have regular TSH tests to check your thyroid hormone levels. TSH tests are also used to monitor your thyroid hormone levels after treatment for hyperthyroidism.
What If I Accidentally Eat Or Drink Before My Blood Test
If you have been instructed to fast before your blood test and you accidentally eat or drink something during the fasting window, it is important to notify your healthcare provider or the person drawing your blood. If you dont, your results could be incorrectly interpreted.
It may be possible for your healthcare provider to interpret the non-fasted test results. Most likely, they will instruct you to reschedule the blood test at a time when you will be able to successfully complete the fast before the test.
Your physician will let you know the steps you need to take before your blood test, including whether or not fasting is required and for how long. By following all testing instructions and best practices , you can ensure a smooth testing process and the most accurate results.
*Post reviewed and approved by Dr. Sona Kirpekar, our in-house Medical Consultant.
Before you go
Why Do I Have To Fast
Nutrients in food and drinks go into your bloodstream and can change things measured by the tests, skewing your results.
For instance, if you eat or drink before a fasting blood glucose test, your blood sugar probably will be higher than if you hadn’t had anything. When you’re fasting, doctors get a baseline result so tests can be compared to give a true picture of your sugar levels over time.
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/6tests That Require Fasting
You do not have to fast for all kind of blood tests. Some can be performed at any time of the day. Here are some tests in which you are required to fast.
Fasting blood glucose test
This test is mostly for diabetic patients to diagnose the amount of sugar in the blood. A fasting blood glucose test is required to know if the glucose level in the body is balanced or not. For this test, one has to fast for 8 to 10 hours.
This test helps to determine the amount of good and bad cholesterol level in the body. High cholesterol level is linked with a different disease like the cardiac issue. One has to avoid foods and liquids other than water for 9 to 12 hours before the test. In some cases fasting is not important, so follow your doctors instructions
Iron blood test
This test is to determine the amount of iron in the blood, which can cause iron-deficient anaemia. You will be asked to fast from the morning and avoid taking any kind of supplement for 24 hours before the test.
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/6why Fasting Is Important
Fasting means to avoid eating and drinking anything before the test is conducted. It is required before some tests for accurate results. Food and fluid are broken down into smaller molecules in our stomach which are later absorbed by the blood. This can alter the level of a certain substance in the blood like sugar, iron, cholesterol.
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Can I Chew Gum Or Brush My Teeth Before The Test
Chewing gum is not allowed because it determines your body to produce digestive fluids. At the same time, the sweetness of the gum can interfere with the blood sugar level. Dont chew gum, but you can brush your teeth, as long as you dont swallow anything. Swallowing toothpaste can start the production of hormones and enzymes in your body, so be mindful of that.
What To Know About Fasting Before Your Lab Test
With certain blood tests, you may be instructed to fast for up to eight hours before your appointment. Fasting before a blood draw means you dont eat or drink anything except water.
Dont wait until the day of your blood draw to ask if you should fast. That could cause your appointment to be rescheduled. If at any point youre unsure if fasting is required, contact your doctor.
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What To Do If You Accidentally Eat Or Drink
If you accidentally ate or drank a sweetened beverage before your test, let your healthcare provider know. Depending on what the test was ordered for, you may be able to go ahead and have your blood drawn, and your healthcare provider will interpret it accordingly.
For example, if you are having a screening cholesterol panel and you ate breakfast before the test, it’s not necessary to reschedule it. In fact, newer recommendations from the National Lipidology Association state that fasting for a screening lipid panel is optional.
While your breakfast will affect the triglyceride level, other important parts of the test, such as the total cholesterol and HDL will not be affected. LDL will only be affected if the triglyceride level is very elevated. If the triglyceride level is elevated, you may be asked to come back to repeat the test.
On the other hand, if a test was ordered specifically for blood sugar and you ate breakfast, the test may not be useful.
Pregnant patients undergoing the glucose challenge test will be asked to fast. If they do not, the test will be rescheduled.
What Are The Tips To Get An Effective Lab Result For Blood Test
The effective lab results depend largely upon your diet and lifestyle. Certain measures by which you can ensure an effective and reliable lab test results include:
- Do not alter your daily routine the day before your sample for the test needs to be collected.
- If you are having some routine blood tests done, then avoid getting them done on the day you feel a little ill.
- Have a normal diet a day prior to the test.
- Follow the fasting regulations given specifically for the test.
- No new exercise or strenuous activity must be started a day before the test.
- If you had a poor night sleep, it is advisable that you reschedule your test.
- The medicines that you take might also affect your test results, so discuss your routine drugs with your doctor.
- Make sure that you stay hydrated at all times.
- Alcohol consumption, smoking, supplements, vitamins and chewing gums must be avoided before the test.
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How To Read Your Results
Your blood will likely be checked using a test called a total lipid profile. To understand your cholesterol test results, youll need to know the different types of cholesterol that the test measures and whats considered normal, potentially risky, and high.
Heres a breakdown of each type. Keep in mind that people who have conditions such as diabetes may need to aim for even lower numbers.
What Do My Creatinine Blood Test Results Mean
Creatinine is measured in milligrams per deciliter of blood . People who are more muscular tend to have higher creatinine levels. Results may also vary depending on age and gender.
In general, however, normal creatinine levels range from 0.9 to 1.3 mg/dL in men and 0.6 to 1.1 mg/dL in women who are 18 to 60 years old. Normal levels are roughly the same for people over 60.
High serum creatinine levels in the blood indicate that the kidneys arent functioning properly.
Your serum creatinine levels may be slightly elevated or higher than normal due to:
- kidney problems, such as kidney damage or infection
- reduced blood flow to the kidneys due to shock, congestive heart failure, or complications of diabetes
If your creatinine is truly elevated and its from an acute or chronic kidney injury, the level wont decrease until the problem is resolved. If it was temporarily or falsely elevated due to dehydration, a very high-protein diet, or supplement usage, then reversal of those conditions will lower the level. Also, a person receiving dialysis will have lower levels after a treatment.
Its uncommon to have low levels of creatinine, but this can occur as a result of certain conditions that cause decreased muscle mass. Theyre usually not any cause for concern.
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What To Expect During Tests
While fasting for blood tests is important, there are other things to know as well. Here is exactly what happens during different tests. Take cholesterol test for example:
A blood test ordered to check your cholesterol levels is usually done in the morning to get accurate results. A lab assistant will clean the puncture site, insert a needle, and draw some blood from a vein. They will also wrap an elastic band around your upper arm before inserting the needle this helps your veins to pop out a bit. After they collect the sample, they will cover the puncture site with a bandage. It usually takes a couple of minutes for the whole procedure to complete.
You do not need to take special care after your test. You can even drive and resume your normal activities immediately after the test. If you have been fasting for the last 12 hours, bring a snack with you to eat after the test. Your doctor will share the test results with you and explain what different values mean. If they find anything abnormal, they may ask you to have another test in a few weeks or months time.
Fasting For Blood Tests: Rules And Guidelines
If your doctor has confirmed that you should not eat anything before the test, you should not ignore their instructions. Here are some guidelines for fasting for a blood tests:
- It is important that you do not eat or drink anything but water. You should not eat anything at least 8 hours prior to your test. It is important to fast for at least 12 hours if your doctor has ordered lipid tests. Water is allowed though.
- You should not chew gum, smoke, or exercise before your test because all these activities can stimulate your digestive system and affect test results.
- Avoid alcohol for at least 24 hours before your test.
- You can take prescription medications unless your doctor advices against it. Certain medications, especially birth control pills can change your cholesterol levels, so you may want to stop taking them for a few days before the test. Your doctor may advise you to take the pills if they want to see its effect on your cholesterol levels.
It is important to note that you should fast for at least 8-12 hours depending on different tests, but avoid fasting beyond 14 hours because it will have a negative effect on the results. Just be sure to drink plenty of water to stay hydrated.
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Which Blood Tests Require Fasting
We all have come across some situation in our lives where we are required to undergo blood test either as a part of a normal checkup or if we are unwell. You may notice, that your clinician advice you to visit the laboratory on an empty stomach. Your physician may advise you some hours of fasting before calling you in to draw blood.
Fasting before a test means that you are not supposed to eat or even drink water for about 8-12 hours before your blood test. You are also not allowed to smoke or chew gum.
Why do they ask you to fast? Which are the blood tests require fasting? What happens if I dont fast? and can we take any medications before fasting blood test? These are some questions clinicians always come across. This article will feed your curiosity regarding fasting for blood tests and will give you an insight into which blood tests require fasting and for how long.
I Accidentally Ate Before A Fasting Blood Test What To Do
If you eat or drink anything but water before a fasting blood test, you should tell the nurse drawing your blood you may have your blood work rescheduled to another day, or they may proceed anyway depending on the case. Also let the doctor who will interpret the results that they may not be accurate because you were not fasting your physician may prescribe the tests again or at least he will be mindful of the possible abnormal results in the report caused by not fasting.
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How Precise Is The A1c Test
When repeated, the A1C test result can be slightly higher or lower than the first measurement. This means, for example, an A1C reported as 6.8 percent on one test could be reported in a range from 6.4 to 7.2 percent on a repeat test from the same blood sample.3 In the past, this range was larger but new, stricter quality-control standards mean more precise A1C test results.
Health care professionals can visit www.ngsp.org to find information about the precision of the A1C test used by their lab.
Testing For Type 1 And Type 2 Diabetes
If diabetes is confirmed by the results of a blood test the type of diabetes you have is usually determined by factors like weight , age at diagnosis, family history and how quickly any symptoms came on.
The test results can also indicate if you are at risk of developing type 2 diabetes even if you dont have it now.
If youre being tested for type 1 diabetes then further blood tests can check your blood ketone levels. Following this you may be sent to hospital for further assessment.
Can I Request My Own Laboratory Tests
You can use QuestDirect to select and pay for lab tests. Licensed professionals from PWNHealth LLC and affiliated professional entities will provide clinical oversight of your lab testing, including ordering your selected tests, when appropriate. Then, have your specimen collected for the testing you purchased. Quest offers testing you can purchase for yourself, with physician oversight, as follows:
- Tests with an In-Person at Quest or In-Person at Drive-Thru option can be purchased in all states except Arizona, Alaska, and Hawaii, as well as Puerto Rico.
- Tests with an At-Home Kit option can be purchased in all states except Arizona, New York , Alaska, and Hawaii, as well as Puerto Rico.
Please note that New York residents may only purchase an at-home kit for a COVID-19 Active Infection Test. New York residents may not purchase any other at-home kits.
We strongly recommend that you share your test results with your doctor in order to make the best health decisions.
Preparing For Your Test
12 hours is the optimal fasting period. Fasting longer than the recommended time could compromise your results. You may be advised to defer the test to another day.
General Fasting information
To ensure your test is accurate it is important to adhere to the following:
- Have nothing to eat or drink for at least 10 to 12 hours preferably an overnight fast
- If you are thirsty, sips of plain water only are permitted. .
- You are advised to avoid smoking
- You are advised not to chew gum
- If you take medication, please continue to take your medication as prescribed
- If you are diabetic please consult your doctor prior to fasting
12 hours is the optimal fasting period, but 10-14 hours is acceptable. Fasting beyond 14 hours affects the quality of the result.
Tips for nervous patients
If blood tests make you nervous, we have special options that will put you at ease.The first step it to let us know how youre feeling. If you have a tendency to become lightheaded when your blood is taken, our staff can have you lie down. This will help you to relax. If you start to feel faint, you can just close your eyes and breathe deeply. Our staff encounter nervous patients all the time are ready to help in any way they can.Practising self-care can also help to ease anxiety.
- Focus on your breathing
- Talk about your family, pets, or things you enjoy
- Try not to hold your breath, tense up or look at the needle.
Visiting our collection centres
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Lists Of Blood Tests That Require Fasting
Administering a lab test may have ample of instructions to be followed. One such is fasting before sample collection. There are a couple of diagnostic tests that require fasting. A bit of alteration from what has been suggested can account for huge erroneous results. So, when you are asked to remain hungry, its better you do it or regret later.
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Health check-ups can be a nerve wreaking experience and full of anxiety at times. Procedures need to be explained and understand clearly so that prior misconceptions can be avoided. Some patients may wonder why fasting is necessary prior to the blood test. Questions that normally comes to mind are: Can the blood sample be taken immediately upon arrival at the hospital or are there any other options available?
Blood Sugar test
Health check-up may require 3 visits to the hospital:
During the first visit, you need to consult a doctor and have an appointment for blood test.
On the second visit which is the test date, you have to fast for 8-14 hours prior to the test, approximately from 8.00 p.m. the night before, until the blood sample is drawn.
There are 2 reasons for 12-hour fasting prior to the blood test
Firstly, fasting blood sugar level is required for diabetes risk analysis . If the result is categorized as pre-diabetes , in accordance to the Clinical Practice Guidelines of the Diabetes Association of Thailand, the oral glucose tolerance test would then be recommended. Those undergoing the test would have to do the following:
need to fast on the test date
drink syrupy glucose solution
have blood sugar test every 30-60 minutes for 2-3 hours
Secondly, fasting is necessary for the following tests:
Blood Lipid test
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