How does a diabetes test work?
Diabetes type 1 as well as diabetes type 2 are chronic diseases with sometimes serious consequences. Therefore, even healthy people are recommended to be tested for diabetes regularly. This is especially true if there have already been cases of diabetes in the family. Some test procedures are also suitable for carrying out at home. Although they do not allow a definite diagnosis, they do provide an indication to pursue further medical examination.
Diabetes test strips
Most pharmacies sell diabetes tests for self-administration. This is a simple version of the urine test that is also performed by a doctor. The test strip is held briefly in the urine stream when urinating. If the test field changes color, sugar is present in the urine.
There are also strip test devices for home use that examine the blood. They are also used by diabetics who regularly inject themselves with insulin. To do this, the patient pricks his fingertip and the drop of blood that comes out is examined for its sugar content.
Diabetes tests do not replace a diagnosis by a doctor!
With diabetes, the metabolism gets out of whack. This leads to symptoms such as increased urination, strong thirst, dry skin, weakness, fatigue and concentration problems – these are often the first warning signs. Advanced diabetes also causes vascular damage, possibly leading to high blood pressure. This is tested and diagnosed at the doctor’s office.
Diabetes risk test
Whether symptoms that occur actually indicate diabetes can possibly be narrowed down by an online test.
A questionnaire of the German Diabetes Foundation and the German Diabetes Society, the so-called FINDRISK online questionnaire, determines the personal risk of developing diabetes within the next ten years. It asks questions about age, family history of diabetes, body weight and diet, and certain laboratory values. Although it is no substitute for a visit to the doctor, it does allow important conclusions to be drawn at an early stage about how the risk of developing diabetes can be reduced.
Diabetes mellitus: How does the doctor test?
A visit to the doctor is essential for a reliable diagnosis of diabetes. The tests are performed either by a family doctor or by a specialist in internal medicine and endocrinology (diabetologist). A detailed preliminary discussion and general physical examination form the basis of the diagnosis. In addition, there are several special examinations:
Measurement of fasting blood glucose
The determination of fasting blood glucose is particularly important for the diagnosis of diabetes. To do this, the doctor takes blood from the patient’s vein and has it tested for sugar. It is important that no food is actually consumed eight hours before the blood sample is taken, which always takes place in the morning, and that at most unsweetened and calorie-free drinks such as tea or water are consumed.
In healthy individuals, fasting blood glucose is below 100 milligrams per deciliter (mg/dl). Values between 100 and 125 mg/dl already indicate a disturbed sugar metabolism (prediabetes), but not yet manifest diabetes mellitus. If fasting blood glucose values measured several times (on different days) exceed 125 mg/dl, the physician diagnoses diabetes mellitus.
A blood sample for the occasional blood glucose can be taken at any time of the day. If the value is repeatedly (at least twice) above 200 mg/dl and the patient has the typical symptoms of diabetes, diabetes mellitus is present.
Oral glucose tolerance test
The oral glucose tolerance test (oGTT) is a diabetes test that more accurately assesses the performance of glucose metabolism. It is not a routine test, but is used when the diagnosis is unclear but impaired glucose metabolism is suspected.
In pregnancy, doctors routinely arrange for the test to detect gestational diabetes in time. However, if diabetes mellitus is already known, they do not use the test to prevent blood glucose levels from rising dangerously.
The oGTT proceeds as follows: The patient first eats a lot of carbohydrates (at least 150 grams per day) for three days and then takes nothing for 12 hours. Blood is then drawn and the fasting blood glucose is determined.
If the blood glucose value is at or above 200 mg/dl after two hours, the diagnosis is “diabetes mellitus. Values between 140 and 200 mg/dl indicate a so-called impaired glucose tolerance, i.e. a preliminary stage of diabetes (“prediabetes”) with already impaired glucose utilization.
Diabetes urine test
A urine examination is also one of the standard tests for diabetes. Normally, there is no or hardly any sugar in the urine because the kidney retains (reabsorbs) it when filtering the blood. However, if the blood glucose level is significantly elevated, the kidney’s ability to reabsorb the glucose is no longer sufficient. The urine therefore contains glucose and the test field on the diabetes test strip changes color.
If the doctor has the urine examined in a laboratory, it is possible to have additional values determined, for example the protein content in the urine. If a diabetes that has not been detected for some time has already damaged the kidneys (diabetic nephropathy), this is often elevated.
HbA1c value
The so-called HbA1c value is that proportion of the red blood pigment hemoglobin that has formed a bond with sugar molecules in the blood – the so-called glycohemoglobin A. In healthy people with permanently normal blood glucose levels, the proportion of HbA1c is below 5.7 percent. However, if the blood glucose values are increased in phases or permanently, the HbA1c percentage also increases. In diabetics, the HbA1c value is at least 6.5 percent.
Antibody test for type 1 diabetes
To diagnose diabetes type 1, the detection of antibodies against the beta cells (islet cell antibodies) or against insulin (insulin antibodies) is also helpful. These auto-antibodies are found in the blood of many affected individuals long before the first symptoms appear.
An antibody test may also be used to distinguish between type 1 and type 2 diabetes – for example, if type 2 unusually occurs in young people.
