Why Do Some Blood Tests Require Fasting
Certain blood tests require you to fast for 8-12 hours. The reason for asking you to fast is because when eat or drink beverages, certain nutrients, substances or vitamins enter into the bloodstream and can be responsible for giving a wrong result. Fasting before these advised blood tests ensures more accurate results.
Certain blood tests require you to not even drink water. Otherwise, drinking normal water will keep you hydrated and prevent your veins from collapsing, so drawing blood becomes easier since your veins are visible.
Avoid food, alcohol, soda or aerated drinks, tea, coffee, chewing gums and even exercising while fasting.
You need to consult your physician if you can take your regular dose of medications during fasting or adjust the dose timings for the purpose of fasting. This is because certain drugs can alter test results.
Ask The Doctor: What Blood Tests Require Fasting
Q.Sometimes my doctor tells me it’s okay to eat before a blood test, and sometimes it isn’t. Why is that?
A. Actually, fasting affects the results of very few blood tests. For example, measurements of kidney, liver, and thyroid function, as well as blood counts, are not influenced by fasting. However, fasting is required before commonly ordered tests for glucose and triglycerides for accurate results.
You should not eat for eight hours before having your blood glucose measured to check for diabetes or to see how well treatments are working. An alternative test for glucose level that does not require fasting measures a substance called hemoglobin A1c, which reflects average blood sugar over the previous three months.
Doctors measure triglycerides after fasting since the concentration of these fatty particles remains elevated in the bloodstream for hours after a meal. The healthy range of triglycerides is less than 150 milligrams per deciliter after a fast of 10 to 12 hours.
Not fasting before a standard lipid panel blood test may also throw off the LDL cholesterol number. But newer methods to measure LDL may mean you dont need to fast. In contrast, eating does not significantly affect measurements of total cholesterol and HDL cholesterol.
When fasting for blood work, you may still drink water, plain coffee, or black tea. Take your regular medications unless you are specifically told to take them only with food.
What Do My Thyroid Test Results Mean
The two most common types of thyroid function tests are the T4 and TSH test. Typically, these two tests are ordered together.
The T4 testmore commonly known as the thyroxine testis used to determine if your thyroid is overactive. If this is the case, you will be diagnosed with hyperthyroidism.
Symptoms of hyperthyroidism include unplanned weight loss, tremors, diarrhea and anxiety.
The TSH test will reveal how much thyroid-stimulating hormone is in your blood. Normal levels range from 0.4 to 4.0 milli-international units of hormone per liter of blood.
If youve been diagnosed with hyperthyroidism and your TSH levels are above 2.0 mIU/L, you are at a heightened risk of developing hypothyroidism, which can result in weight gain, fatigue, depression and weak hair and nails.
If your doctor believes you have hyperthyroidism, he or she may order a T3 test to check for levels of the hormone triiodothyronine.
This hormone level should be within 100-200 nanograms of hormone per deciliter of blood. If your levels are abnormally high, it is possible that you are suffering from an autoimmune disorder called Graves disease.
The final thyroid function test your doctor may order is the T3 resin uptake test. Also known as a T3RU, this blood test will measure the binding capacity of a hormone called thyroxin-binding globulin.
Your doctors office should reach out to you within a matter of days to walk you through the results of your thyroid test.
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Things That Can Affect Your Thyroid Function Results
MedicationsSome medications can interfere with your results, so it’s important to tell your doctor about any drugs you take.
PregnancyBeing pregnant can also influence your results. So if you’re pregnant, make sure to discuss this with your doctor.
Time of dayYour circadian rhythm can slightly affect your TSH levels. This means that the time of day you do your blood test could affect your results. TSH typically peaks in the early hours of the morning, drops to lower levels mid-morning, and increases again in the early evening. How much your levels will change really depends on you as an individual.
We Need Insulin To Make Many Hormone Conversions
Once a month adding in these carbs , we magically start converting our hormones and feeling better! This applies to the rest of the month. This is imperative for those people with thyroid conditions. Fasting and diet variation are both great ways to increase your thyroid health, in conjunction with my multi-therapeutic approach to healing.
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How Many Hours Prior Do You Need To Fast For A Thyroid Blood Test
A common question regarding thyroid tests is something along the lines of do you need to fast for a thyroid blood test. According to doctors and medical practitioners, no special precautionary measures are to be taken before getting a thyroid blood test. In fact, in many cases, doctors object to fasting before a thyroid blood test. Research suggests that TSH test results during fasting, or early morning without breakfast, show different results compared to those obtained on a full stomach, in the afternoon. It is suggested to not fast before a thyroid blood test, as it provides misleading results of increased TSH levels in the body.
However, if you are undergoing some health tests other than thyroid blood tests and fasting is required, you may consult your doctor and fast for 8-10 hours before getting the test done. Always remember that fasting for a blood test excludes drinking water.
What Are Thyroid Function Tests
If your provider suspects you are having problems with your thyroid, he or she may recommend a thyroid function test.
These simple blood tests are used to determine how well your thyroid gland is working based on your hormone levels.
There are four different types of thyroid function tests: T3, T3RU, T4 and TSH.
If your provider is concerned about the levels of your hormones, broad screening tests, like the T4 or the TSH test will be ordered.
Further tests may be needed to help determine whats going on if the results of these tests come back abnormal.
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What Medications Can Affect The Thyroid Panel Tests
Many multivitamins, supplements , and over-the-counter and prescription medications may affect thyroid test results and their use should be discussed with your healthcare practitioner prior to testing. For example, biotin can interfere with some lab tests, so your healthcare practitioner may advise you to refrain from taking biotin or supplements that contain biotin for a few days before having blood drawn for a thyroid panel.
Abnormal Results Of A Thyroid Blood Test
Since the most frequent concern, do you need to fast before a thyroid blood test has been addressed, let us move on to the three types of results of a thyroid blood test. Your thyroid blood test either shows a healthy result or an abnormal result . In the latter results, an abnormal result could be due to thyroid malfunction indicating either of the two hypothyroidism and hyperthyroidism
A case where a high concentration of thyroid hormone is present in the blood is known as hyperthyroidism. Conditions that lead to this alleviation of blood thyroid hormone may include:
- Excessive iodine
- Thyroid Nodules
On the other hand, a condition where a lower than normal concentration of thyroid concentration is present in the blood is called hypothyroidism. Conditions that can lead to a decreased value of thyroid hormone in blood include:
- Iodine deficiency
- Hashimotos thyroiditis
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Questions For Your Doctor About Test Results
When you review the results of your TSH test with your doctor, it could be helpful to ask specific questions, such as the following:
- Is my level of TSH within the normal range?
- Do my test results suggest that my thyroid is overactive or underactive?
- What additional tests will you be ordering, if any?
When Is It Ordered
A thyroid panel may be ordered when you have signs and symptoms that suggest underactive thyroid or overactive thyroid due to a thyroid disorder.
Signs and symptoms of an underactive thyroid may include:
- Trouble tolerating heat
- Sometimes more frequent bowel movements
- Some uncommon problems that can affect the eyes: puffiness around the eyes, dryness, irritation, excessive tearing, light sensitivity, blurry double vision
- In some cases, bulging of the eyes
- Less frequent or lighter menstrual periods in women
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Interpreting Thyroid Function Test Results
While normal ranges may vary from lab to lab, generally each hormone should fall within a reference range that is considered normal. Acceptable ranges are:
-
TSH: 0.4-4.5 mIU/mL
-
Tg Ab: < 1.0 IU/mL
Some institutions may use narrower ranges depending on how the blood is analyzed in the lab. When looking at your results, typically there is a reference range listed so you know if the measurement is normal for that specific lab.
If your results are outside the normal range, this may indicate temporary fluctuations in thyroid function rather than a longer-term thyroid condition. And day-to-day variation in levels can be normal and part of a healthy, responsive endocrine system.
What Is It Used For
A TSH test is used to find out how well your thyroid is working. It can tell if you have hyperthyroidism or hypothyroidism in your blood. But a TSH test can’t show what is causing a thyroid problem.
If you take prescription thyroid hormone medicine because of hypothyroidism or because you had your thyroid removed, you’ll 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.
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What Is The Thyroid
Located on the lower part of the front of the neck, the thyroid is a butterfly-shaped gland that measures two inches in length. For men, the gland is located underneath the Adams apple, near the windpipe.
The thyroid, which is part of the endocrine system, is responsible for the metabolism.
When there are no issues with the thyroid, and its a normal size, it cannot be felt however, when it doesnt work right, it may become enlarged or could grow lumps of extra tissue.
What Is Reverse T3
Reverse T3 is a biologically inactive form of T3. Normally, when T4 is converted to T3 in the body, a certain percentage of the T3 is in the form of RT3. When the body is under stress, such as during a serious illness, thyroid hormone levels may be outside of normal ranges even though there is no thyroid disease present. RT3 may be elevated in non-thyroidal conditions, particularly the stress of illness. It is generally recommended that thyroid testing be avoided in hospitalized patients or deferred until after a person has recovered from an acute illness. Use of the RT3 test remains controversial, and it is not widely requested.
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What Do Thyroid Function Tests Measure
Thyroid function tests check levels of hormones and antibodies in the blood. And, most of the time, a provider will order several of these tests together to get the overall picture of your thyroid function.
Here are the different types of thyroid tests, what they measure, and the role they play in your thyroid health:
What Can A Thyroid Test Detect
- What Can a Thyroid Test Detect?
When most people hear about the thyroid, they associate it with the inability to lose or gain weight, but it is responsible for much more than that.
In fact, hormones made by the thyroid can impact how quickly your heart beats, how deep you breathe, your body temperature, womens menstrual cycles and cholesterol levels.
Unfortunately, more than 12 percent of people will deal with a thyroid problem in their life, with women being more likely to deal with this issue than men.
Heres what you need to know about the thyroid and what a test can detect.
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Do I Need To Fast For My Thyroid Test
Usually,no special precautions including fasting need to be followed before taking a thyroid test. However, your pathologist can guide you better. For example, if you have to undergo some other health tests along with thyroid hormone levels, you may be asked to fast for 8-10 hours. Drinking water doesnt come under violation of fasting.
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There Are Two Things I Know When It Comes To Achieving And Maintaining Good Health: Fasting Is Second To None And Having A Healthy Thyroid Function Is A Must Can Fasting And Thyroid Conditions Coincide
Thyroid conditions can have a tremendous impact on a persons health and are on the rise: Autoimmune thyroid affects millions, and oftentimes goes undiagnosed. According to theNational Cancer Institute, there were 53,990 estimated new cases of thyroid cancer in 2018, with rates for new cases rising on average 3.1% each year over the last 10 years. Death rates have been rising as well, 0.7% each year over 2006-2015.1
According to the National Institute of Diabetes and Digestive Kidney Diseases, other thyroid conditions are problematic as well: approximately 4.6 percent of the U.S. population ages 12 and over has an underactive thyroid 2, and 1 person out of 100 in the U.S. have an overactive thyroid 3.
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Thyroid Function Test Normal Values
Most common blood tests for thyroid are TSH, T4 and T3. Blood samples taken usually measures free or active T3 and T4. Thyroid test uses reference ranges to compare the results with the normal healthy population. Reference ranges for healthy thyroid are:
Test From To Units
TSH 0.4 4.0mU/l
FT4 9.0 25.0pmol/l
FT3 3.5 7.8pmol/l
Blood Test To Manage Thyroid Disorder
The blood test for TSH is used to assure that your thyroid hormones level is satisfactory and under control. As increased levels of thyroid can adversely affect the cardio system in the long run so it must be under check before it is too late. In case of thyroid cancer efforts are made to keep the patients TSH level below the thyroid function test normal values .
In the initial stages of treatment, the blood tests for thyroid are referred every week as to keep a close check on the thyroid levels. In case of hypothyroidism a TSH test will be preferred whereas in hyperthyroidism TSH test and T4 test are suggested. The frequency of test depends upon the severity aspect of the patient case history.
Measures before thyroid test?
Blood test for thyroid can be influenced either because of medications or illnesses. Thyroid function test normal values can be influenced widely due to some significant reasons:
When to have a thyroid test?
When A person is prone to thyroid?
How lifestyle affects thyroid
What are the Blood Tests for Thyroid? was last modified: February 10th, 2020 by Team Dr Lal PathLabs
Is Thyroid Curable Permanently
Yes, there is a permanent treatment for hyperthyroidism. Removing your thyroid through surgery or destroying your thyroid through medication will cure hyperthyroidism. However, once your thyroid is removed or destroyed, youll need to take thyroid hormone replacement medications for the rest of your life.
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When Do You Need A Thyroid Test
When your body has too little or too much thyroid hormone in the blood, it shows obvious symptoms. In cases where the thyroid hormone in your blood is lesser than normal , you may observe one or more of the following symptoms:
- Puffiness or soreness in different parts of the body
- Tremors in hand
If you present with any of the above-mentioned symptoms, whether for hyperthyroidism or hypothyroidism, and suspect that you have thyroid dysfunction, we suggest getting a thyroid blood test. Read ahead to find out whether you need to fast for a thyroid blood test.
How Is The Test Used
A thyroid panel may be used to evaluate thyroid function and/or help diagnose thyroid disorders.
Typically, the preferred initial test for thyroid disorders is a TSH test. If the TSH level is abnormal, it will usually be followed up with a test for free T4. Sometimes a total T3 or free T3 will also be performed. Often, the laboratory will do this follow-up testing automatically. This is known as reflex testing and it saves the healthcare practitioner time from having to wait for the results of the initial test and then requesting additional testing to confirm or clarify a diagnosis. Reflex tests are typically performed on the original sample that was submitted when the initial test was requested.
As an alternative, a thyroid panel may be requested by your healthcare practitioner. This means that all three tests will be performed at the same time to get a more complete initial picture of thyroid function.
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What Is Being Tested
A thyroid panel is a group of tests that may be ordered together to help evaluate thyroid gland function and to help diagnose thyroid disorders. The tests included in a thyroid panel measure the level of thyroid hormones in the blood.
A thyroid panel usually includes tests for:
Although rarely used these days, sometimes a T3 resin uptake test is included. T3RU and T4 can be used to calculate a free thyroxine index . This is another method for evaluating thyroid function. It corrects for changes in certain proteins that can affect total T4 levels.
The thyroid is a small butterfly-shaped organ that lies flat across the windpipe at the base of the neck that produces thyroid hormones, primarily T4 and some T3. These hormones travel throughout the body and regulate the metabolism by telling the cells in the body how fast to use energy and produce proteins. Most of the hormone produced by the thyroid is T4. This hormone is relatively inactive, but it is converted into the much more active T3 in the liver and other tissues.
Almost all of the T3 and T4 circulating in the blood is bound to protein. The small portions that are not bound are called free and are the biologically active forms of the hormones. Lab tests can measure the amount of free T3 or free T4 or the total T3 or total T4 in the blood.
The body has an elaborate feedback system to control the amount of T4 and T3 in the blood.