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When to take a glucose test and how to prepare for it?

 Kiedy wykonać badanie glukozy i jak się do niego przygotować?

You're tired, constantly thirsty and craving a sweet dessert after eating. Or do you notice weight loss and visit the toilet more often? If so, get tested for diabetes. This dangerous disease, if left untreated, can lead to nerve damage, blood vessels or cataracts. In extreme cases, it causes coma or death. From this article, you will learn when you should test your glucose levels and how to prepare for the test.

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When should a glucose test be taken?

Glucose is your body's primary source of energy. Most carbohydrates from meals are absorbed into the bloodstream precisely in the form of glucose. The blood sugar concentration, or glycaemia, is tested mainly to diagnose pre-diabetes and diabetes.

Symptoms that should concern you include:

  • dry mouth, increased thirst
  • frequent urination, especially at night
  • sudden deterioration of vision
  • wounds that take a long time to heal
  • recurrent infections
  • increased appetite, including for sweet foods
  • weight fluctuations unrelated to diet
  • weakness, drowsiness, anxiety.

Fasting glucose testing is also worth doing if you are at risk of:

  • you are overweight or obese
  • you have excessive abdominal fat accumulation
  • you have hypertension or heart disease
  • you avoid physical activity
  • a sedentary lifestyle
  • someone in your family has diabetes.

Underdiabetes, or hypoglycaemia, is also a threat to health and life. Early symptoms that may indicate too low a blood sugar level are:

  • a feeling of hunger
  • nausea
  • weakness
  • pallor
  • dilated pupils
  • restlessness
  • cold sweats.

Over time, these symptoms may be accompanied by:

  • orientation disorders
  • speech disorders
  • convulsions
  • coma.

Some of the causes that can affect low blood sugar levels include:

  • undiagnosed diabetes
  • vomiting
  • diarrhoea
  • intense physical exertion or poor diet.

Also, people with diabetes can have low blood sugar levels, for example when the dose of insulin given is too high in relation to the meal eaten.

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Prepare for glucose testing

Glucose testing is a laboratory test. A blood sample taken from the patient is tested. Testing blood glucose levels at home with a blood glucose meter does not give diagnostic results. The reason for this is that the value obtained on a home glucose meter may have a measurement error of up to 15% of the result.

The body's diurnal rhythm influences the fluctuations in blood sugar levels, so it is important to follow your doctor's recommendations, according to which you will do:

  • fasting glucose test - do not eat or drink (except water) 8 hours before the test
  • postprandial glucose test - taken two hours after a meal (pregnant women are tested after 1 hour)
  • Glucose testing at any time - an abnormal result is not a diagnosis of diabetes and requires further testing.

Before the test, tell your doctor about all the medicines and dietary supplements you are taking. This is because some of them may affect your blood sugar levels. Your diabetologist will decide whether it is necessary to stop taking your medicines early when referring you for tests.

Pregnancy and glucose testing

When to do a glucose test during pregnancy? If you are pregnant, your doctor will order a fasting blood glucose test and an oral glucose load test (OGTT) to diagnose gestational diabetes.

Which women are at risk?  The risk group associated with diabetes, includes women who have a body mass index (BMI) above 30, which means obesity.

Women over 35 years of age are also in the risk group. Those who have had a baby weighing 4.5 kg or more in a previous pregnancy are also worth mentioning. Diabetes can affect women who have a history of gestational diabetes - they should be more vigilant and monitor their blood sugar levels.

Women with at least one parent or sibling with diabetes also have a higher risk of developing diabetes. There are also ethnic groups, such as Latinos and African-Americans, who have an increased risk of diabetes.

The OGTT test involves drawing blood from a vein for testing:

  • fasting
  • after drinking glucose
  • 60 minutes after drinking glucose
  • 120 minutes after drinking glucose.

You may experience drowsiness, nausea, weakness or dizziness between blood draws. This is due to the sudden release of insulin after drinking glucose.

When to see a diabetologist?

To ensure that the time spent on testing is not time wasted, invest in a visit to a specialist. It is very important to consult a diabetologist about your test results.

We wrote more about diabetes and what a diabetologist can help with here.

If you have worrying symptoms or are concerned about a test result and do not want to stand in a long queue to see an in-patient specialist, use online diagnostics. The sooner you talk to your doctor about your test results, the more effective the care they will be able to give you and decide how to proceed.

Glucose testing - how often to do it

Patients who have not been diagnosed with diabetes should prophylactically perform a fasting glucose test at least once a year! 

The frequency varies when referring to patients who have already been diagnosed with diabetes. For multiple insulin injections, patients are advised to take at least four glucose measurements per day. This way, you monitor your blood sugar levels and adjust your insulin dose according to your body's needs. Measuring fasting glucose will help you assess how your body is responding to insulin. 

For diet-only treatment, fasting measurements are recommended once a month and two hours after the main meals. In addition, patients should take measurements once a week at different times to monitor the variation in blood sugar levels throughout the day.

Patients taking oral medication should have their glucose measured once a week at fasting and after meals, and one measurement at different times each day. Fasting measurement allows assessment of the initial blood sugar level, and post-meal measurement allows monitoring of the effect of meals on blood sugar levels. Daily measurements at different times allow assessment of the variability of blood sugar levels throughout the day. 

If you are taking fixed doses of insulin, take fasting and post-meal measurements once a week. Daily measurements allow you to monitor the variability of your blood sugar levels throughout the day, and a daily glycaemic profile provides a detailed picture of your blood sugar levels.

How to prepare for a glucose test?

It is necessary to take a blood sample from the patient. Glucose levels in the body fluctuate throughout the day, so it is recommended that the test is carried out in the morning, on an empty stomach. This means that the patient should not eat or drink anything for approximately 8-12 hours before the test (water is permitted). It is also advisable to limit or completely refrain from physical exercise before the test.

Before the blood sample is taken, the patient will rest for 10-15 minutes. If the blood sample is taken under stress, this may affect the test result by increasing the blood glucose level. The patient's final preparation schedule for the glucose test should be determined by the attending physician.

Glucose testing and results - what is the standard

Glycaemic results can fall within different ranges, depending on the patient's condition. Normal values are between 70 and 99 mg/dl (3.9-5.5 mmol/l). A fasting blood glucose level between 100 and 125 mg/dl (5.6-6.9 mmol/l) is considered abnormal.

If the fasting blood glucose level is above 126 mg/dl (7.0 mmol/l), the patient may have diabetes. However, this alone is not enough to make a diagnosis, an additional test is required - the OGTT test, which takes 120 minutes. This test assesses how the patient's body manages glucose uptake and whether they have diabetes.

The final interpretation of blood glucose results should be made by the doctor in charge, who will take into account a number of factors, such as the patient's age, health status, type of treatment provided and other risk factors associated with diabetes.

What the glucose and insulin test results may mean?

Have you obtained results between 100 mg/dl and 125 mg/dl (5.6-6.9 mmol/l)? In your case, a diagnosis of so-called abnormal fasting glycaemia is made, which requires an additional test - an oral glucose tolerance test (OGTT). This allows your doctor to assess your condition more accurately and to plan further medical treatment. 

There are several factors that can influence elevated blood glucose levels, such as pregnancy, thyroid disorders, various types of pancreatic disease, certain cancers, taking certain medications or inadequate preparation for the test. It is therefore important that the attending physician consults the results of the test with the patient and carefully considers any factors that may have influenced the result.

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Cost of glucose testing

The price of a glucose and insulin test may vary depending on the location of the laboratory or blood collection point. In Poland, the price of a glucose test is usually between 9 and 18 PLN. In some cases, prices may be higher, especially in private clinics and laboratories. However, it is worth bearing in mind that many medical facilities offer testing packages in which the price for a glucose test may be lower than when performed separately. In addition, patients using public services receive glucose testing under the National Health Service, without incurring the cost.

What else we can do for you?

Diabetes is one of the most common diseases of civilisation. It is important to detect it early and treat it in close cooperation with a diabetologist. Self-monitoring is an important part of the treatment of diabetes, but the doctor decides on the treatment. Remember that fluctuations in blood sugar levels do not necessarily mean that you have diabetes, but they should prompt you to see a specialist.

If you have noticed symptoms in yourself or someone close to you that are described in the text, make a standard appointment with a diabetologist.

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