Why Doctors Order It
A fasting blood glucose test is done to screen for prediabetes and diabetes. It also helps doctors monitor diabetes and determine if medications and dietary changes are having an effect .
Your fasting blood glucose level is the lowest your blood sugar can be because the influence of recent meals is minimized .
Fasting blood sugar is often checked alongside HbA1c , which is a measure of your blood sugar levels over the past three months. The more sugar there is in the blood, the more it will attach to hemoglobin, raising HbA1c .
Taken together, the two offer more information than each test alone. For example, even if your blood sugar levels are very high at one random point, they may have been mostly low over the past couple of months . On the other hand, HBA1c could be higher but your glucose levels at the moment lower.
Apart from diabetes, abnormal levels can point out issues such as insulin resistance, hormonal imbalances, and pancreatic, liver, or kidney disease.
What Happens If You Dont Fast Before Blood Test
Not fasting for a blood test will yield inaccurate results. As mentioned above, as the food is digested and metabolized, the nutrients which enter the bloodstream can interfere with test results.
If you happen to accidentally eat or drink something before a blood test, make sure to inform your clinician about it. In this case, both the clinician makes a note of it and test results are analyzed accordingly or you for better results, an appointment for the blood tests may need to be rescheduled.
Blood Sugar Levels At Night
It’s also important to check your blood sugar before bedtime. According to the Joslin Diabetes Center, your before-bed blood sugar should be between 90 and 150 mg/dL. If your level is lower than this, you may need to have a small snack to prevent your blood sugar from falling too low overnight.
If you notice that your morning blood sugar levels are high, it may be due to something called the Somogyi effect, according to the Cleveland Clinic. This phenomenon occurs when blood sugar levels drop too low overnight, prompting the liver to release stored glucose to “rescue” you. If your doctor suspects that you are experiencing the Somogyi effect, he or she may ask you to check your blood sugar between 2 and 3 a.m. for several nights in a row. If your overnight sugars are indeed too low, your doctor will help you come up with a plan to manage the situation.
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Can I Eat And Drink Before Having A Blood Test
It depends on the type of blood test you’re having. The healthcare professional arranging your test will tell you if you need to do anything to prepare for it.
You can eat and drink as normal before some blood tests. But if you’re having a “fasting blood test”, you will be told not to eat or drink anything beforehand. You may also be told not to smoke before your test.
How Do I Take Care Of My Blood Glucose Meter
- Set the date and time when you get a new meter.
- Make sure the date and time are right each time you use your meter.
- Use the control solution as needed. This will let you know the meter and test strips are working right. Use it:
- When you get a new meter.
- When you get new test strips.
- When you think that the meter is not giving you the right blood glucose number.
That Number You See In Your Glucose Meter After Eating Is Very Important
The non-fasting value of blood sugar levels can indicate the possibility of prediabetes or diabetes.
The timing of non-fasting blood glucose levels is important, says Alison Massey, MS, RD, LDN, registered dietitian and certified diabetes educator with over 10 years of experience in various community and clinical settings.
Typically, if someone has diabetes we suggest they monitor before meals and sometimes post-prandially which should be less than 180 mg/dL.
Monitoring a pre- and a two-hour after meal blood glucose provides individuals with diabetes a better idea of how the food they are consuming is impacting their blood glucose level.
How Is Hypoglycemia Diagnosed
A medical diagnosis of hypoglycemia typically requires satisfying the “Whipple triad.” These three criteria include:
- Documented low glucose levels , often tested along with insulin levels and sometimes with C-peptide levels)
- Symptoms of hypoglycemia when the blood glucose level is abnormally low
- Reversal of the symptoms when blood glucose levels are returned to normal
Primary hypoglycemia is rare and often diagnosed in infancy. People may have symptoms of hypoglycemia without really having low blood sugar. In such cases, dietary changes such as eating frequent small meals and several snacks a day and choosing complex carbohydrates over simple sugars may be enough to ease symptoms.
Random Blood Sugar Test
This measures your blood sugar at the time youre tested. You can take this test at any time and dont need to fast first. A blood sugar level of 200 mg/dL or higher indicates you have diabetes.
|140 mg/dL or below||N/A|
*Results for gestational diabetes can differ. Ask your health care provider what your results mean if youre being tested for gestational diabetes.Source: American Diabetes Association
If your doctor thinks you have type 1 diabetes, your blood may also tested for autoantibodies that are often present in type 1 diabetes but not in type 2 diabetes. You may have your urine tested for ketones , which also indicate type 1 diabetes instead of type 2 diabetes.
What Is The A1c Test
The A1C test is a blood test that provides information about your average levels of blood glucose, also called blood sugar, over the past 3 months. The A1C test can be used to diagnose type 2 diabetes and prediabetes.1 The A1C test is also the primary test used for diabetes management.
The A1C test is sometimes called the hemoglobin A1C, HbA1c, glycated hemoglobin, or glycohemoglobin test. Hemoglobin is the part of a red blood cell that carries oxygen to the cells. Glucose attaches to or binds with hemoglobin in your blood cells, and the A1C test is based on this attachment of glucose to hemoglobin.
The higher the glucose level in your bloodstream, the more glucose will attach to the hemoglobin. The A1C test measures the amount of hemoglobin with attached glucose and reflects your average blood glucose levels over the past 3 months.
The A1C test result is reported as a percentage. The higher the percentage, the higher your blood glucose levels have been. A normal A1C level is below 5.7 percent.
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Who Should Do The Test
According to the American Diabetes Association, screening for diabetes is recommended in people over 45 , or at any age if you have certain risk factors, including :
- Being overweight, obese, or physically inactive
- Having a close relative with diabetes
- Belonging to a certain race/ethnic group
- Having signs of insulin resistance or conditions associated with insulin resistance, such as high blood pressure , low good cholesterol and/or high triglycerides , and polycystic ovary syndrome
- Having had diabetes in pregnancy
What About Fasting For A Blood Test During Pregnancy
There are several blood tests you may need if youre pregnant. These are designed to assess any potential health concerns that you or your baby might experience during pregnancy or after you give birth. Some of these tests will require you to fast beforehand. Your doctor will advise you how to prepare for each test.
Fasting is usually safe if youre pregnant, provided youre in good health and arent having a high-risk pregnancy. For your overall comfort, your doctor may advise you to drink extra water or to remain indoors, especially if the weather is very hot or humid.
Fasting may increase heartburn in some pregnant women. If you experience uncomfortable or concerning symptoms of any kind while youre waiting to have your blood drawn, let your doctor know immediately.
If youre seeing a doctor other than your obstetrician-gynecologist, make sure they are made aware of your pregnancy before your blood test.
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Is Diabetes Diagnosed The Same Way In Every Country
There are four methods of diagnosing diabetes, which are used around the world. They are:
Can Urine Samples Be Tested For Glucose
Urine samples are routinely tested for glucose as part of a urinalysis. Additional testing is usually done to identify the cause of an abnormal urine glucose result.
Glucose usually only shows up in the urine if glucose is at sufficiently high levels in the blood that some of the excess is lost in the urine, or if there is some degree of kidney damage and the glucose is leaking out into the urine.
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Is A Fasting Blood Sugar Of 110 Too High
Blood Sugar Levels After a Fast
Increased levels are linked to diabetes and insulin resistance, a condition in which the body is unable to adequately manage sugar . Values to aim for: Normal is less than 100 mg/dL. If your fasting glucose level is between 110 and 125 mg/dL, you have impaired fasting glucose
A1c Results And What The Numbers Mean
|Diabetes||6.5 percent or above|
When using the A1C test for diagnosis, your doctor will send your blood sample taken from a vein to a lab that uses an NGSP-certified method. The NGSP, formerly called the National Glycohemoglobin Standardization Program, certifies that makers of A1C tests provide results that are consistent and comparable with those used in the Diabetes Control and Complications Trial.
Blood samples analyzed in a doctors office or clinic, known as point-of-care tests, should not be used for diagnosis.
Having prediabetes is a risk factor for developing type 2 diabetes. Within the prediabetes A1C range of 5.7 to 6.4 percent, the higher the A1C, the greater the risk of diabetes.
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What Abnormal Results Mean
If you had a fasting blood glucose test:
- A level of 100 to 125 mg/dL means you have impaired fasting glucose, a type of prediabetes. This increases your risk of developing type 2 diabetes.
- A level of 126 mg/dL or higher usually means you have diabetes.
If you had a random blood glucose test:
- A level of 200 mg/dL or higher often means you have diabetes.
- Your provider will order a fasting blood glucose, A1C test glucose tolerance test , depending on your random blood glucose test result.
- In someone who has diabetes, an abnormal result on the random blood glucose test may mean that the diabetes is not well controlled.
Other medical problems can also cause a higher-than-normal blood glucose level, including:
- Overactive thyroid gland
- Swelling and inflammation of the pancreas ( pancreatitis
- Stress due to trauma, stroke, heart attack, or surgery
- Rare tumors, including
- Weight loss after weight loss surgery
- Vigorous exercise
Some medicines can raise or lower your blood glucose level. Before having the test, tell your provider about all the medicines you are taking.
For some thin young women, a fasting blood sugar level below 70 mg/dL may be normal.
How To Check Blood Sugar Without A Meter
Diabetes is a chronic condition where the body either doesnt make enough insulin or doesnt use insulin properly or both. This can lead to a higher than normal blood sugar level.
Uncontrolled blood sugar levels can lead to complications, such as:
- heart disease
- nerve damage
For these reasons, its important to monitor your blood sugar if you have diabetes.
Prior to using meters, people with diabetes would monitor their blood sugar by testing their urine. This method, however, wasnt as accurate, nor did it provide real-time results.
If you self-test your blood sugar several times a day using a glucometer, or meter, it requires that you prick your finger to draw blood to test. Due to the discomfort of this method, you might look for a way to monitor your level without this tool.
If finger pricks are very bothersome for you, dont worry theres hope. Advances in blood sugar monitoring technology could mean no more finger pricks in the future.
If you have diabetes, there are several portable devices you can use to check your blood sugar level and not all of them require a finger prick.
Things That Can Affect A Fasting Blood Sugar Test
A fasting blood sugar level is usually ordered by a physician either to check for a new diagnosis of diabetes or to monitor a person who is known to have diabetes, according to the Mayo Clinic.
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Blood sugar, also known as glucose, is the body’s main source of energy. A fasting blood sugar level is a measurement of how much glucose is in a person’s blood after 12 hours without eating or drinking anything other than water, according to the Cleveland Clinic. That’s why this simple blood test is usually done in the morning, before breakfast. If your fasting blood sugar is high, it is likely a sign of diabetes.
In order to understand what can affect a fasting blood sugar level, it’s helpful to know a bit more about how the body processes glucose.
The body gets most of its glucose supply from metabolizing the carbohydrates in food, per Kaiser Permanente. Insulin, a hormone produced by the pancreas, helps move glucose out of the bloodstream and into the cells, lowering blood sugar levels in the process. But people with diabetes have systems that either don’t make enough insulin or can’t use the insulin that they do have effectively. This leads to high blood sugar, or hyperglycemia.
Fasting Blood Sugar Test Results
Here are the possible outcomes of a fasting blood sugar test, according to the Mayo Clinic:
- Normal fasting blood sugar: less than 100 milligrams per deciliter
- Impaired fasting glucose : between 100 and 125 mg/dL
- Diabetes: greater than 126 mg/dL
How Long Should I Fast Before Blood Test
You are required to fast for up to 12 hours before going for a blood test. Drinking coffee, tea or even water can affect blood test results.
Avoid Over Fasting, this particularly applies to diabetic individuals and pregnant women. Over fasting can cause dehydration and hypoglycemia in diabetics. Over fasting can also sometimes alter test results.
Make sure to carry some snacks to your physicians office so that you can eat immediately after blood is drawn. Blood glucose for postprandial levels requires you to eat and give a blood sample after an hour of a meal.
Hopefully, this article has given you a good idea about fasting for blood tests and which blood tests require fasting. These questions should additionally be clarified with your physician. This is because your physician will be able to guide you better.
Medically Reviewed By
Dr. Himanshi is a Homoeopathic consultant and currently working as a lecturer in Post-graduate faculty of Homeopathy, Parul University, Vadodara. Completed BHMS and MD in Homeopathy in January 2018 and also has a clinical experience of about 6 years. Personal interests include reading, spending time with family and traveling.
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What Number Should My Blood Glucose Be
Blood glucose is measured in mg/dl. The normal range for blood glucose for people without diabetes is 70 to 120 mg/dl.
The Diabetes Center has guidelines for blood glucose readings. This is called a target range. There may be times when your healthcare provider gives you a different target range, like for bedtime, with exercise, or after eating.
Nationwide Childrens Hospital Diabetes Center Target Blood Glucose Ranges
The goal is to keep the blood glucose within the target range most of the time.