Diagnostic analysis of diabetes mellitus

"Detecting a disorder such as diabetes in time can help avoid complications arising from its evolution over time".


Diabetes mellitus is primarily characterized by the presence of high concentrations of glucose in the blood (hyperglycemia).

This is due to the alteration in the action of insulin or absence of this hormone, which is produced in the pancreas to allow the capture of glucose by the tissues that use it as fuel.

Type 1 diabetes mellitus is due to the destruction of autoimmune origin of the pancreas' b cells and leads to absolute insulin deficiency.

In a high percentage of the patients antibodies against b cells (ICAs), antiinsulin antibodies (AAI) and antiglutamic acid decarboxylase (GAD) are detected.

These antibodies can sometimes be detected before the appearance of the disease, which gives them a great predictive interest.

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When is the diagnosis of diabetes made?

There are several diagnostic tests that are performed to determine whether or not you have diabetes.

They consist of the collection of blood or urine samples and subsequent analysis to determine glucose levels. In some tests, a certain amount of glucose is ingested and the body's ability to metabolize it is measured.

New methods of continuous monitoring of glucose in the interstitial space are a major advance in the management of these patients.

By means of a minimally invasive technique, such as inserting a sensor into the anterior wall of the abdomen, glucose values are obtained for approximately 72 hours without interruption.

This system makes it possible to evaluate glycemic fluctuations in order to improve metabolic control.

Most frequent indications of this test:

  • Diabetes mellitus type 1.
  • Diabetes mellitus type 2.
  • Gestational diabetes.

Do you have any of these diseases?

You may need to have a diagnostic test for diabetes

Types of diagnostic tests for diabetes

Plasma glucose

The presence of glucose in concentration above 200 mg/dl. (11.1 mmol/l.) in fasting venous plasma is compatible with the diagnosis of diabetes mellitus if it has occurred at least twice without other cause.

Values below 115 mg/dl. (6.4 mmol/l.) rule out the diagnosis.

It should be noted that the blood glucose level is lower in venous blood than in arterial and capillary blood (blood obtained by pricking the fingertip), so that the glucose level is determined by the point of blood extraction.

Urinary Glucose

If the blood glucose limit is exceeded, which is between 160 and 180 mg/dl. (9-10 mmol/l.), glucose passes into the urine, which is known as exceeding the renal threshold.

As a diagnostic test it has a very limited value because of the changing degree of dilution it can have.

However, its analysis is of interest within routine urinary tests for the detection of alterations.

This test tries to measure our body's ability to metabolize glucose. It is the main diagnostic test for diabetes mellitus.

It consists of subjecting the body to a standard amount of glucose. It is performed with 75 g of oral glucose or with 1.75 g/kg of weight up to 75 g in the case of children. It is accompanied by 400 ml. of water and is ingested in 5-10 minutes. According to the expert groups, a basal sample should be extracted and another at 2 hours.

Normally, if there is good absorption, the curve should exceed 200 mg/dl at some point, and normalize after 120 minutes, with values below 140 mg/dl.

A state of glucose intolerance is considered to be reversible with appropriate treatment if, at the 120-minute point, the plasma glucose concentration is between 140 and 200 mg/dL. Above this limit, the result is compatible with a state of diabetes mellitus.

It is performed during the sixth or seventh month of pregnancy and aims to rule out or early detect the states of diabetes during pregnancy that in a very significant number will lead throughout life in cases of diabetes mellitus.

A blood sample is taken one hour after ingesting 50 g. of glucose. It should not exceed 140 mg/dl. If it is for diagnosis, 200 g. are administered and basal samples are obtained after 1, 2 and 3 hours.

The maximum normal levels are 105, 190, 165 and 145 mg/dl, respectively.

Both in the basal extraction and after the overload it can be interesting to know the changes of the plasma insulin.

C-peptide (inactive fragment released by the pancreas in a ratio of 1:1 to the hormone) can be used to assess residual pancreatic insulin production if the patient injects insulin.

In type 1 diabetes mellitus, the production of the hormone is practically nil, while in type 2 diabetes mellitus it tends to be elevated in order to overcome tissue resistance to its action.

Where do we do it?


The Clinical Biochemistry Service
of the Clínica Universidad de Navarra

The Clinical Biochemistry Service of the Clinica Universidad de Navarra is responsible for performing the biochemical analyses requested by the medical specialists of our center.

We carry out technical quality controls to guarantee the proper functioning of the equipment and the highest precision in the results obtained from the samples.

In order to guarantee excellence in patient service, we offer the response with the results of the analyses in the shortest possible time, responding in only 46 minutes in some cases of general analysis.

Organized in care units

  • General biochemistry.
  • Electrolytes.
  • Hormones, urine and proteins.
  • Markers.
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Why at the Clinica?

  • Maximum speed in offering the analytical results.
  • We carry out quality controls to guarantee the correct and most precise results obtained.
  • We work in a multidisciplinary way with all the departments of the Clinic.