Glucose Test

Overview

The glucose test is also known as the sugar test. This test detects the presence of glucose in blood. This is a diagnostic test to detect diabetes. There are different types of sugar tests available.

  • Random sugar test
  • Fasting Sugar
  • Postprandial
  • Glucose tolerance test

If a person is diabetic then, another test HbA1c, is performed every 2 to 6 months, depending on their condition. 

Diabetics

It is a condition where our body is unable to utilise the glucose present in food. A hormone produced by our body called insulin is responsible for making glucose available to the cells. Diabetics results when the hormone is defective or when it is not working properly. There are two types of diabetics.

  • Type I diabetics 
  • Type II diabetics

HbA1c

Glycated hemoglobin is also known as HbA1c . This test is a diagnostic test for type II diabetics and also for monitoring glucose control in type I diabetics. The iron-containing protein in the RBC is called Hemoglobin; it is responsible for the red color of the RBCs. The main function of hemoglobin is to carry oxygen to all parts of the body. Glucose binds to RBC and remains attached to it until the RBC’s are alive. 

The HbA1c test measures the number of glycated RBC in the blood. This gives the trend of sugar levels for 3 months, as the lifespan of a normal RBC is 90 days. 

Symptoms

Generally, when a person has the following symptoms or conditions, the physician might order a test of his blood glucose levels.

  • Increased thirst
  • Increased urination
  • Tiredness
  • A wound that does not heal in time
  • Unexpected weight loss
  • Numbness in the feet and hands
  • Fainting
  • Unexplained hunger
  • High body mass index (BMI)
  • Family history of diabetics
  • Pregnancy
  • Above the age of 45
  • Physical inactivity

Sample collection

For the glucose test, either one of the samples is collected.

  • Capillary blood: this sample is collected to test the random glucose levels in a person. There is no specific time for performing a random sugar test. No need to fast. Blood from the fingertips is collected. A needle prick is made, and blood is collected.
  • Venous blood: in this method, blood from the veins is collected. A small needle is inserted in the veins, and blood is collected in a syringe. This type of sample collection is performed for fasting blood glucose level, postprandial glucose level, glucose tolerance, and HbA1c tests. 

Precautions to be taken

Fasting of at least 10—12 hours is necessary for fasting sugar testing; for postprandial, blood has to be collected within 90 minutes of food intake. For the glucose tolerance test, after the collection of blood for the fasting test, a glucose solution is given to the person, and blood is collected at an interval of one hour for the next 2-3 hours. 

Results and interpretations

TypesFastingPostprandial
Recommended blood glucose levels 
Normal or healthy individual72—100 mg/dLBelow 140 mg/dL
Prediabetic100—125 mg/dL140—199 mg/dL
DiabeticMore than 126 mg/dLMore than 200 mg/dL
Children with type I diabetes72—126 mg/dL90—162 mg/dL
  • The normal sugar levels are fasting sugar below 100 mg/dL and postprandial sugar value of less than 140 mg/dL.
  • If the fasting values are 100—125 mg/dL and postprandial sugar levels are 140—190 mg/dL, then the person is prediabetic. This means that the person has an increased chance of becoming diabetic if there are other high-risk conditions like obesity, genetics, and physical inactivity. This can be reversed by dieting, taking less carbohydrates, and following a more protein diet. Also, being physically active will  help in reducing the sugar levels. 
  • If the fasting blood sugar is above 126 mg/dL and the postprandial is above 200 mg/dL, then the person has diabetes. If the sugar levels are more, advice from a physician is necessary for further action. Also, consuming healthy foods and engaging in regular physical activity help to maintain sugar levels. Managing sugar levels in diabetics is necessary, as high sugar levels can affect the liver, kidney, brain, heart, and eyes. 
  • If the sugar levels are lower than normal, then the condition is called hypoglycemia, this can be due to the medicine if the person is diabetic. If the person is not diabetic, low sugar can be because of an underlying disease like liver disease, kidney disease or underactive pituitary, thyroid, or adrenal glands. Low sugar levels are not common, and it can affect the brain.

HbA1c

TypesRecommended levels
Healthy or normal individualBelow 5.7%
Prediabetic5.7% to 6.4%
Diabetic6.5% and higher

If the HbA1c is in the prediabetic range, then the person has to take the test every 6 months, and regular physical exercise and diet can help to bring the levels back to normal.

If the results are in the diabetic range, then the person is advised to take the test every 3 months to manage diabetes. 

Glucose tolerance test

This test is mainly performed to diagnose gestational diabetics, i.e., diabetics during pregnancy. During the 26-28 th week of pregnancy, this procedure is performed. Initially, the person’s blood sample is collected, and their sugar level is tested. After this, 75 ml of glucose solution is given, and after an hour, blood is collected and sugar levels are tested. If the levels are high, then the person has to repeat the test with a higher dosage of glucose solution, probably 100 ml, and blood drawn every hour for at least 2 to 3 hours. The recommended values are the same as for diabetics. If the sugar levels are above 140 mg/dL, then the person is prediabetic, and if it is above 200 mg/dL, the person has diabetes.

Reference

  1. https://medlineplus.gov/lab-tests/blood-glucose-test/
  2. https://www.diabetes.co.uk/diabetes_care/blood-sugar-level-ranges.html
  3. https://www.healthdirect.gov.au/hba1c-test#:~:text=HbA1c%20is%20a%20blood%20test%20that%20is%20used%20to%20diagnose,carries%20oxygen%20through%20your%20body.
  4. https://www.ncbi.nlm.nih.gov/books/NBK549816/#:~:text=For%20an%20HbA1c%20test%20to,HbA1c%20of%206.5%25%20or%20higher.
  5. https://www.mayoclinic.org/tests-procedures/glucose-tolerance-test/about/pac-20394296

Written by Krishnambal.S

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