Diagnosis of diabetes

For centuries diabetes was diagnosed by the doctor dipping his finger into a urine sample and tasting it to detect abnormal sugar levels. The treatment was sometimes just as weird - in 1690 doctors prescribed 'gelly of viper's flesh', 'broken red coral', 'sweet almonds' and 'fresh flowers of blind nettles'. Things have moved on and diagnosing and treating diabetes is now a lot easier!

Type 1 diabetes symptoms normally develop very rapidly, sometimes over a couple of weeks. They tend to be more severe. Type 2 diabetes symptoms are normally milder and develop gradually. These symptoms are caused by the effect of diabetes on the body.

If the level of glucose in the blood becomes too high, excess glucose is removed from the blood by the kidneys and excreted via the urine (glycosuria). This results in greater urine production and causes the patient to urinate frequently. Water held in the cells is required to replace lost blood volume, and thus causes dehydration and thirst.

View the sections within the interaction below to learn more about the signs and symptoms of diabetes, the effect it has on their blood chemistry and the tests performed to diagnosed diabetes.

What are the main symptoms for type 1 diabetes?

There are the major indicators of diabetes:

  • polyuria - the need to urinate frequently
  • polydipsia - increased thirst & fluid intake
  • polyphagia - increased appetite
  • weight loss
  • tiredness.

Symptoms of type 1 diabetes can develop quickly, over weeks or even days.

What are the other major signs of diabetes?

  • Blurred vision - A change in glucose absorption can bring about a change in the shape of the lens in the eye, leading to an altered vision quality. This can cause blurred vision, a common complaint that can indicate type 1 or type 2 diabetes.
  • Diabetic ketoacidosis - Diabetic ketoacidosis occurs when the body begins to break down stores of fat as an alternative source of energy, leading to a build-up of acids in the blood known as ketones. This can result in weight loss and muscle wasting. Diabetic ketoacidosis is a very rare complication of diabetes. Ketoacidosis can result in coma and possibly death if left untreated.

Other symptoms are:

  • itchiness around the vagina or penis or getting thrush regularly
  • cramps
  • constipation
  • skin infections

What are the main symptoms for type 2 diabetes?

In type 2 diabetes the signs and symptoms are not always obvious as the condition develops slowly over a period of years. It may only be picked up in a routine medical check-up. The common symptoms are:

  • tiredness
  • poor healing process
  • malaise
  • sometimes weight gain or weight loss
  • thirsty and nocturia
  • dry mouth.

Thirst and polyuria will develop as hyperglycaemia progresses, particularly in the elderly. It is important to be vigilant for the signs and symptoms of diabetes as early diagnosis and treatment can reduce the risk of developing complications later. Many people have type 2 diabetes for years without knowing it because early symptoms can be general.

What happens when a person develops diabetes and reports these symptoms?

If you or your patient suspects that these symptoms may indicate diabetes then it needs to be correctly diagnosed before treatment can be given. It is important to be vigilant for the signs and symptoms of diabetes and pre-diabetes when treating patients, and to diagnose as early as possible so that treatment can be started. In the case of pre-diabetes early diagnosis could mean that the condition could be prevented. Today you would most commonly check blood glucose levels using a meter rather than urine testing. Diabetes is often missed in the elderly. According to the World Health Organisation, someone may have diabetes if they have:

  • an HbA1c of 48mmol/l (6.5%) or above is a diagnostic of diabetes in most situations (2 tests)
  • a fasting blood glucose of 7 mmol/L or more, OR
  • a blood glucose 11.1 mmol/L or more after a 2-hour oral glucose tolerance test. (GTT)

Someone has impaired glucose tolerance if they have:

  • a fasting blood glucose of less than 7 mmol/L, AND
  • a blood glucose of 7.8 mmol/L or more but less than 11.1mmol/L after a 2-hour oral GTT.

Someone has impaired fasting glycaemia if they have:

  • a fasting blood glucose between 6.1 to 6.9 mmol/L, AND
  • a blood glucose of less than 7.8 mmol/L after a 2-hour oral GTT.

Tests to diagnose diabetes and pre-diabetes

HbA1c Blood test

HbA1c has become the most common method of diagnosing diabetes, as recommended by WHO. This test measures recent average blood glucose level. The test measures a part of the red blood cells. Glucose in the blood attaches to part of the red blood cells. This part can be measured and gives a good indication of an average blood glucose over the previous 2-3 months. A blood sample is required. An HbA1c of 48mmol/l (6.5%) or more is a diagnostic of diabetes in most situations. HbA1c is also used to monitor diabetes in a patient and will normally be done every 2-6 months. Patients with diabetes aim to lower the HbA1c level to below a target level normally around 48-53 mmol/mol (6.5% - 7.0%, NICE guidelines). However, individualisation of the target goal level will be negotiated between the patient and their diabetes team, as the levels may vary for each patient.

When it cannot be used:

  • children and young people
  • if patient is suspected of having type 1 diabetes
  • patients has symptoms of diabetes for less than two months
  • patients who are acutely ill
  • if patient is taking medication that may cause rapid glucose rise, for example steroids
  • patient has acute pancreatic damage, including pancreatic surgery.
  • pregnancy
  • patients with abnormal red blood cells such as Thalissaemia.

Random blood glucose test

In a medical emergency, when a patient (most often a child) has such high glucose levels that they are drifting in and out of a coma, a blood glucose reading can be found by taking a blood sample to measure the glucose with no consideration to when the last meal was eaten. A level of 11.1 mmol/L or more in the blood sample indicates diabetes. A further blood glucose test will need to be done to confirm the diagnosis.

Fasting blood glucose test (FBG)

The FBG test is taken using a blood sample obtained following a period of fasting (so no food or drink, except water) of at least eight hours. The fast normally starts from midnight. A sample of blood is taken early the next day, before food or drink. A level of 7.0 mmol/L or more after an overnight fast indicates diabetes. To confirm the diagnosis, it is usually necessary to repeat the test a second time on a different day.

Oral glucose tolerance test (OGTT)

For this test the patient fasts from midnight and then a baseline fasting blood glucose test is taken. The patient then consumes a drink that contains 75g of glucose (lucozade is normally used) and then they wait for 2 hours before their blood glucose is measured again. This test is different from the others as the patient drinks a sugary drink as a way of measuring how the pancreas manages the glucose. In a person without diabetes glucose levels rise and fall quickly, as the body naturally produces insulin to lower the blood glucose. A person with diabetes will see a sharp rise and a sustained high level of glucose. This is because the pancreas is unable to deliver the needed insulin to lower the glucose in the blood. A blood glucose level of 11.1 mmol/L or more in the blood sample taken after two hours indicates diabetes.

Urine test for glucose

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 that is dipped into a sample of the patient's urine. Colour changes on the strip show whether there is glucose in the urine sample. Some people have kidneys that are more 'leaky', and glucose may leak into urine with a normal blood level. If a patient's urine contains any glucose a blood test should be carried out to measure the blood level of glucose to confirm, or rule out, diabetes.

Whether a fasting glucose, random glucose or HbA1c is used to test for diabetes it will generally need repeating as there should be evidence of 2 results using the same testing method to confirm diagnosis test.

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