Diabetes mellitus

After reading this chapter you should be able to:

  • assess, diagnose and manage diabetes and its complications, including diabetic ketoacidosis

  • assess, diagnose and manage hypoglycaemia in the child with diabetes

The diagnosis of diabetes has a significant impact on children, young people and their families. Like all other chronic conditions, it will affect the physical and mental health of the individual and may influence many life choices. All paediatric teams will need skills in the management of patients admitted acutely with the major metabolic abnormalities seen with diabetes whilst the long-term support, advice and monitoring is provided by specialist diabetes teams. Such teams include paediatricians, dieticians, nurse specialists and psychologists and will have experience in the management of biochemical, physical, emotional and behavioural difficulties seen in patients with diabetes.

The most common form of diabetes mellitus in children and young people is type 1 diabetes which is a polygenic disease due to the autoimmune destruction of insulin-producing pancreatic beta cells. Other types of childhood diabetes include type 2 diabetes (the result of multiple gene abnormalities and environmental factors) and monogenic diabetes (due to various single gene defects) Diagnostic criteria are shown in Table 24.1 .

Table 24.1

The recognised diagnostic criteria for diabetes mellitus

Random blood glucose (in the presence of typical symptoms) greater than 11.1 mmol/l
Fasting plasma glucose level greater than 7 mmol/l
2-hour post prandial glucose greater than 11.1 mmol/l
HbA1c greater than 48 mmol/mol (6.5%)
An abnormal random blood glucose (> 11.1 mmol/l) in the presence of typical symptoms is diagnostic. However, children and young people who are asymptomatic need a second abnormal result on another day to confirm the diagnosis
Impaired glucose tolerance
Fasting plasma glucose greater than 7.0 mmol/l
2-hour post prandial glucose greater than 7.8 mmol/l and less than 11.1 mmol/l
Impaired fasting glucose
Fasting plasma glucose 6.1 to 6.9 mmol/l

Diabetes is a lifelong condition, and those young people who receive their initial care from paediatric teams will need to transfer to adult services at some stage in their teenage years. Such a transition needs careful planning by both paediatric and adult teams, and the patient and their family need to be guided on the process before it occurs. The actual transition should occur at a time of relative stability in the health of the young person and should aim to avoid major events in lifestyle and education such as school exams.

Type 1 diabetes mellitus

Clinical presentation

Typical symptoms of diabetes are polyuria, polydipsia and polyphagia, weight loss and recurrent infections. The individual may be relatively well or may present very unwell with diabetic ketoacidosis (DKA) with marked dehydration, shock and a reduced conscious level.

The risk of developing other autoimmune conditions such as hypothyroidism, thyrotoxicosis, coeliac disease, Addison disease and autoimmune liver disease is higher in children with type 1 diabetes when compared to the general population.


Children and young people with the clinical features suggestive of diabetes mellitus should be referred on the same day to secondary care for urgent assessment and the initiation of insulin therapy. This is to avoid any delay and risk the child developing DKA.

Investigations in hospital setting include:

  • random blood glucose

  • blood ketones

  • urea and electrolytes—to asses dehydration and electrolyte disturbance

  • blood gas—to assess if acidosis

  • thyroid function test

  • coeliac screen (tissue transglutaminase)

  • diabetes related auto antibodies—may aid differentiation of type of diabetes

Treatment and management

Those who are alert, well and not vomiting should be encouraged to take oral fluids. They will also need to start insulin either as multiple daily insulin injections or as a continuous subcutaneous insulin infusion. Both approaches will need the required total daily dose of insulin to be calculated using 0.5–0.75 units/kg/day. Patients will need basal insulin, pre-meal bolus insulin and correction dose prescribed ( Table 24.2 ).

Table 24.2

Calculation of daily insulin requirements

Basal insulin Between 30% to 50% of total daily dose (TDD) is given as basal insulin using a long-acting insulin analogue (Glargine, Determir or Insulin degludec)
Pre-meal insulin The pre-meal insulin bolus using rapid-acting insulin analogue (Insulin Aspart, Insulin Lispro, Insulin Glulisine) and is prescribed as insulin:carbohydrate ratio (I:CHO ratio)
There are different ways to calculate the I:CHO ratio
Some clinicians use the ‘500 rule’ (500/TDD) for children over 5 years and ‘300 rule’ (300/TDD) for those under 5 years. Some hospitals use pre-set I:CHO ratios rather than using either 500 or 300 rules.
Correction dose This is the amount of extra rapid-acting insulin analogue to administer to bring high glucose levels to target
To calculate the ‘correction’ dose:

  • calculate the child’s Insulin Sensitivity Factor (which is how much 1 unit of insulin will reduce their blood glucose in 2–4 hours) by dividing 100 by the total daily dose of insulin (100/TDD).

  • determine the required fall in glucose level to return the value to the target range

  • calculate the number of units of insulin which will produce this required fall in glucose level

For example, if the calculated Insulin Sensitivity Factor for a particular patient is 4, the measured blood glucose is 11 mmol/l and target blood glucose is between 4–7mmol/l, this indicates that the patient will need to administer an extra 1 unit of insulin to bring their measured blood glucose into the top end of the target range (7 mmol/l). An extra 1.5 units would bring the measured blood glucose towards the lower end of the range (5 mmol/l).

The prescribing of insulin must be undertaken with care and the UK Department of Health and Social Care has identified errors in the prescribing of insulin as ‘never events.’ It is therefore important that:

  • the words ‘unit’ or ‘international units’ should not be abbreviated

  • specific insulin administration devices should always be used to measure insulin (i.e. insulin syringes and pens)

  • insulin should not be withdrawn from an insulin pen or pen refill and then administered using a syringe and needle

The blood glucose targets are:

  • on waking: 4–7 mmol/l

  • before meals: 4–7 mmol/l

  • after meals: 5–9 mmol/litre

  • when driving: at least 5 mmol/l

The overall aim is to achieve good glycaemic control without disabling hypoglycaemia or undue emotional distress. An HbA1c of less than 6.5% (48 mmol/mol) and a ‘Time in Range’ of over 70% is associated with reduced risk of developing long-term vascular complications. Children should monitor their glucose levels at least 4–5 times a day. Some wear continuous glucose monitors (CGM) that measure interstitial, rather than blood, glucose levels continuously but displays the readings every 5 minutes.

Practice Point—administration of insulin in a young person recently diagnosed with diabetes mellitus type 1

A 14-year-old boy is admitted via his GP and is diagnosed with type 1 diabetes. He is well and weighs 44 Kg.

  • Total daily dose (TDD) of insulin is calculated as 44 x 0.75 = 33 units

  • Basal insulin dose = 50% of TDD = 16.5 units

  • Insulin: Carbohydrate Ratio = 500/TDD = 15. Insulin:CHO ratio = 1 unit:15 gm CHO (Some hospitals use a set Insulin:CHO ratios based on age or weight instead of using the ‘500’ rule)

Correction Dose : Calculate insulin sensitivity (ISF) = 100/TDD = 3.0

Calculating Pre-meal bolus Insulin

If he wishes to consume a meal containing 30 g of carbohydrate and his pre-meal blood glucose is 11 mmol/l, he will calculate the amount of pre-meal insulin needed to address both of these issues separately and bring his glucose level within target blood glucose of 4–7 mmol/l

  • Insulin:CHO ratio —to accommodate 30 g CHO meal needs 2 units (30/15)

  • Correction dose —to reduce his BG from 11 mmol/l to 5 mmol/l needs 2 units (2 x 3.0)

Total Pre-meal insulin dose = 4 units

All children and young people and their families should be taught by dietitians about the need for healthy eating and carbohydrate counting skills at diagnosis. Families should be taught to recognise patterns of high or low blood glucose and how to use the information to adjust insulin dosages to achieve their glycaemic targets.

Fasting blood glucose levels reflect the action of the basal insulin and if patient has a pattern of high fasting blood glucose, then the basal insulin dose will need to be increased to bring the glucose level into target range. The pre-meal blood glucose levels reflect the action of the insulin analogue injected in the preceding meal; for instance, the blood glucose before lunch reflects the action of the pre-breakfast insulin analogue whilst the glucose level before evening meal reflects the action of the pre-lunch insulin analogue and the glucose level before bedtime reflects the action of the pre-evening insulin analogue.

Practice Point—insulin adjustment

The father of a 7-year-old girl with type 1 diabetes rang for advice as her blood glucose profile has been erratic. She currently takes 6 units of glargine before bed. Her pre-meal insulin: carbohydrate (I: CHO) ratio is 1:10 before breakfast and 1:15 before lunch and evening meal. Her blood glucose profile is shown.

Date Blood glucose levels in mmol/l
Before breakfast Before lunch Before evening meal Before bed
12/11 6.0 2.5 7.1 6.3
13/11 5.7 3.6 4.7 5.6
14/11 5.9 3.4 5.1 6.3
15/11 6.3 3.0 6.3 5.9

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Jul 31, 2022 | Posted by in PEDIATRICS | Comments Off on Diabetes mellitus

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