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How Long To Fast Before Blood Sugar Test


What Is The Fasting Blood Sugar Test Used For

Fasting for Blood test| How Long Fast Before Glucose and cholesterol test

The fasting blood sugar test is also used to test the effectiveness of different medication or dietary changes on people already diagnosed as diabetic

Fasting blood sugar levels are measured by taking a blood test after a period of fasting, usually of 8 hours without food. Typically, fasting blood glucose levels are taken in the morning before any breakfast is eaten. When having your fasting blood glucose levels take, you should not have any drinks apart from water during the period of fasting.

A fasting blood glucose test can be useful to see how well the body is able to manage blood sugar levels in the absence of food. When we do not eat for several hours, the body will release glucose into the blood via the liver and, following this, the bodys insulin should help to stabilise blood glucose levels.

A fasting blood glucose test therefore shows:


  • Whether the body is able to bring down the raise in blood glucose levels from the previous meal
  • How effectively the body copes with its own release of glucose

The target for fasting blood glucose levels are the same as the targets for before meal readings.

  • For adults with diabetes, the target level is between 4 and 7 mmol/l
  • For children with diabetes, the target level is between 4 and 8 mmol/l

However, ;some people may be set individual targets, by their doctor, that differ to the above levels.

A Need To Update Older Guidelines

Aldasouqi also points out that specialists currently recognize that eating before undergoing a blood cholesterol test is unlikely to affect relevant measurements. Therefore, having a meal before going in for a test may actually be better than fasting and potentially losing consciousness on the way to the laboratory.

He adds that the idea of fasting before a blood test comes from antiquated sets of guidelines from the 1970s, which specialists in Canada and most European countries no longer use.

For this reason, he says that United States-based specialists may want to consider revising their own guidelines to better fit the needs of their patients.


According to the studys findings, only 35 percent of participants had received advice about how to prevent a FEEHD event before going in for a blood cholesterol test.

We encourage patients who receive orders for a lab test, explains Aldasouqi, to ask their doctor if fasting is really necessary, and if so, how they should handle their diabetes medications during the fasting period to account for the changes in their blood sugar levels.

FEEHD is overlooked in clinical practice, and we aim to bring this problem to light and further educate doctors and patients about the consequences of fasting while on diabetes medications, he adds.

Why It Is Done

Blood glucose tests are done to:

  • Check for diabetes.
  • Monitor treatment of diabetes.
  • Check for diabetes that occurs during pregnancy .
  • Determine if an abnormally low blood sugar level is present. A test to measure blood levels of insulin and a protein called C-peptide may be done along with a blood glucose test to determine the cause of hypoglycemia. To learn more, see the topic C-Peptide.

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Diabetes And The Blood Glucose Test

Type 1 diabetes is usually diagnosed in children and teenagers whose bodies arent able to produce enough insulin. Its a chronic or long-term condition that requires continuous treatment. Late-onset type 1 diabetes has been shown to affect people between the ages of 30 and 40.

Type 2 diabetes is usually diagnosed in overweight and obese adults, but it can develop in younger people as well. This condition occurs when your body doesnt make enough insulin or when the insulin you produce doesnt work properly. The impact of type 2 diabetes may be reduced through weight loss and healthy eating.

Gestational diabetes occurs if you develop diabetes while youre pregnant. Gestational diabetes usually goes away after you give birth.

After receiving a diagnosis of diabetes, you may have to get blood glucose tests to determine if your condition is being managed well. A high glucose level in a person with diabetes may mean that your diabetes isnt being managed correctly.

Other possible causes of high blood glucose levels include:


Can You Eat Before Any Blood Test

Fasting Before a Blood Test: How Long to Fast and More

Many types of blood tests dont require you to fast. A healthcare provider will let you know if, and for how long, you need to avoid eating.

For all types of blood tests, including fasting tests, you can still drink plain water. You should avoid other drinks like coffee, tea, juices, and alcoholic beverages.

The following tips may help make fasting for your blood test easier:

  • Stay hydrated. Drinking plenty of water before your test makes your blood vessels easier to find.
  • Schedule a morning test. If your blood test is in the morning, youll likely only need to skip one meal.
  • Eat before fasting. Eating directly before your fasting window reduces the amount of time you need to avoid food. For example, if your test is at 9 a.m. and you need to fast for 12 hours, you may want to eat your last meal around 8:30 p.m. the night before.
  • Avoid exercising during your fast. Exercise speeds up digestion and causes you to burn extra calories.
  • Keep yourself distracted. Keeping yourself busy may help take your mind off your hunger.

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Diagnostic Conventions And Covariates

The fasting state was defined by a fasting duration of at least 8;h. Smoking was defined as current smoking or as a history of cigarette smoking during the past year. Physical inactivity was set by <2;h/week. The time since last caloric intake was calculated by generating the difference between the time of blood withdrawal and time of last caloric intake whereas missing data for one of the two variables was excluded.


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Is There Anything Else I Need To Know About Fasting Before A Blood Test

Be sure to talk to your health care provider if you have any questions or concerns about fasting.

You should talk to your provider before taking any lab test. Most tests don’t require fasting or other special preparations. For others, you may need to avoid certain foods, medicines, or activities. Taking the right steps before testing helps ensure your results will be accurate.

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How Long Is Fasting Required Before Blood Tests

The amount of time you need to fast depends on the type of test youre receiving. A doctor will tell you how long you should abstain from eating.


  • Blood glucose test. A fasting blood glucose test usually requires an overnight fast that lasts for about 8 to 10 hours.
  • Blood cholesterol test. Some types of cholesterol tests dont require fasting. Some like a direct LDL cholesterol test may require up to a 14-hour fast.
  • Triglyceride level test. You likely wont need to fast for a triglyceride test, but a 12-hour fast may be required in some situations.
  • Serum iron test. You may be requested to fast for 12 hours and to avoid taking iron supplements for 24 hours before this test.
  • Vitamin B12 tests. Youre often not required to fast before a vitamin B12 test. In some situations, a doctor may recommend a fast thats about 6 to 8 hours.
  • Vitamin B complex test. A blood test looking at all your B vitamins is typically performed the morning after an overnight fast.
  • Renal function panel. You may be told to fast for 8 to 12 hours before a renal function test.
  • Gamma-glutamyl transferase test. A doctor may instruct you to fast overnight and avoid alcohol for 24 hours.

What Is A Fasting Blood Glucose Test

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Your body converts the carbohydrates, which you eat into glucose.

Glucose testing is primarily done for people with;type 1 diabetes,;type 2 diabetes, and;gestational diabetes. Diabetes is a condition that causes your blood glucose levels to rise.

The amount of sugar in your blood is usually controlled by a hormone called;insulin. However, if you have diabetes, your body either doesnt make enough insulin or the insulin produced doesnt work properly. This causes sugar to build up in your blood. Increased levels of blood sugar can lead to severe organ damage if left untreated.

In some cases, blood glucose testing may also be used to test for;hypoglycemia. This condition occurs when the levels of glucose in your blood are too low.

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Best Times Of Day To Check Your Blood Sugar

Your blood sugar can change constantly throughout the day. Checking your blood sugar with test-strips or an FBGM several times throughout the day is just as important as taking your medications.

For example, checking your blood sugar before breakfast tells you how well your body is managing during the 8 hours you were asleep, but it doesnt tell you how well your body handles meals.

Here, well look at the best times to check your blood sugar for the most information about your diabetes management!

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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How Should You Prepare For An Hdl Test

Your doctor will give you complete instructions on how to prepare for the test. These may include not taking certain medications for a short period or fasting for up to 12 hours before the test.

You shouldnt have an HDL test when youre sick. Cholesterol levels are temporarily lower during acute illness, immediately following a heart attack, and during stressful events like surgery or an accident. Its recommended that you wait at least six weeks after any illness before you have your cholesterol measured. In women, HDL cholesterol can also change during pregnancy. You should wait at least six weeks after having a baby before your HDL is measured.

Why Is Fasting Required Before Blood Tests

Fasting & Blood Test

Fasting before a blood test helps improve the accuracy and reliability of the test. Accurate test results are a critical component of diagnosing various health conditions and monitoring the effectiveness of treatment plans.;

Your diet contains a range of nutrients, including carbohydrates, proteins, fats, minerals and vitamins. When you eat and drink normally, those nutrients are broken down and absorbed into your bloodstream. This can impact the levels of those substances in the blood and skew lab test results.

For example, certain methods of diabetes testing measure the patients baseline blood sugar levels after a period of fasting. Eating directly before the test will cause the patients blood sugar to spike, leading to an inaccurate test result. The patient could be misdiagnosed with prediabetes or diabetes, unless their doctor recommends that they complete a second test.


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Can I Have Lemon Water While Fasting

Is lemon water safe to drink while fasting? In strict terms, consuming any number of calories will break a fast. That said, human metabolism is complex and doesnt operate like an on-and-off switch . In reality, drinking plain lemon water, which contains minimal calories, is unlikely to affect your fast.

What To Do If You Broke Your Fast

If you break your fast, the results of your test may be inaccurate. You can call your doctor to see if the test can still be done.

Some tests may be still be analyzed knowing that youre not in a fasted state. Its important to be honest with the test administrator so they can interpret your results properly. Some types of tests may need to be rescheduled.

There are many conditions a doctor might want to test for using a fasting blood test. Just three of many examples include diabetes, high cholesterol, or low iron.


The following early symptoms may indicate you have one of these conditions:

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Which Blood Tests Require Fasting Beforehand

Everyone is bound to get blood work done at some point in their lives. Whether it be a general check-up or a screening for possible diagnoses, blood tests reveal significant insights about our health. For instance, a blood test can determine if someones iron levels are deficient or within the normal range, as well as any other nutrient.;

Fasting is the abstention from food and beverages for 8-12 hours before a blood test. It is a standard procedure for patients to conduct prior to a blood draw. However, each blood test differs, and it is essential for a phlebotomist to learn which tests require fasting, whether or not the patient can drink liquids, and the fasting periods length. That way they can inform a patient about what they need to do to prepare for their blood test in order to have accurate results.;

Using The Same Finger All The Time

What is fasting blood sugar?

People choose to use the same finger and the same spot in part because everyone has a favorite, says Uelmen, and also because calluses build up and cut down on the discomfort. But varying your fingers is better.


The solution for better diabetes control: “The goal is to use a different finger each day or each time,” she says. Switching fingers allows the pricked finger to heal and also helps to avoid pain caused by repeat jabs.

If your blood sugar readings are generally consistent, you can even try alternate site testing, such as using the palm of your hand, if you want to get away from your fingers periodically. But simply using different spots on the same finger can also prevent soreness.

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What To Expect During The Test

The HDL test is quick and relatively painless. A healthcare provider will draw a blood sample using a needle. Youll feel the sting of the needle where the blood sample is taken. Some tests, such as home tests, only need a drop of blood taken using a small needle called a lancet.

When they draw enough blood into the airtight bottle attached to the needle, theyll package the sample and send it to a laboratory for testing. If you feel woozy or lightheaded after the blood draw, you may rest and possibly have a snack or a sugary drink to help you feel better.


How To Maintain Healthy Fasting Blood Sugar Levels

It is Important to Follow A Healthy Diet to Keep Fasting Blood Sugar Levels from Rising High. Some Tips Include:

  • Lowering sodium intake
  • Reducing or completely avoiding sweetened snacks
  • Choosing whole-grain bread and pasta over low-nutrient and high-calorie white bread and pasta
  • Eating fiber-rich foods which help lower the blood glucose
  • Eating high-protein foods which help keep you feeling fuller and avoid mid-meal snacking

People on diabetic medication who are prone to experience sudden dips in blood sugar should follow a similar diet, and also take proactive steps to prevent such incidences. These include:

  • Having regular meals
  • Increasing food intake and having frequent snacks during higher than normal physical activity
  • Limiting or completely avoiding alcohol
  • Consulting a physician in case of vomiting or diarrhoea

Thus, a fasting blood sugar test done at regular intervals will help the patients and the doctors with a deeper understanding of the patients diabetes status and how the medications prescribed for the condition are helping the patient. Diabetes requires constant monitoring and the treatment may be needed to be changed over time. Diabetics can help themselves by maintaining a detailed health log and staying committed to the dietary and lifestyle changes prescribed by the doctor.

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Fasting Before A Blood Test: Drinking Coffee Eating And More

Certain blood tests require fasting beforehand. If your healthcare provider has instructed you to fast before your upcoming test, it means that you should not eat or drink anything for the specified amount of time before having your blood drawn.

Understanding why fasting is important and how to properly fast before a blood test can be helpful for eliminating pre-test anxiety and simplifying the testing process. Below, learn how to fast for a blood test correctly to help make sure that your test results are accurate.;

Urine Test For Blood Sugar

Fasting Before a Blood Test: How Long to Fast and More

Urine does not normally contain glucose. The kidneys filter our blood, keeping substances the body needs, while getting rid of waste products. Your kidneys constantly reabsorb glucose so that it doesn’t enter your urine. However, if the glucose level goes above a certain level, the kidneys can’t reabsorb all of the glucose. This means that some glucose will ‘spill’ through the kidneys into the urine.

A simple dipstick test can detect glucose in a sample of urine. In a dipstick test a doctor or nurse uses a special chemical strip which he/she dips into a sample of your urine. Colour changes on the strip show whether there is glucose in the urine sample. If you have glucose in your urine, you are likely to have diabetes.

However, some people have kidneys that are more ‘leaky’ and glucose may leak into urine with a normal blood level. Therefore, if your urine contains any glucose, you should have a blood test to measure the blood level of glucose to confirm, or rule out, diabetes.

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