Dr Aidin Rawshani

Normal blood sugar levels


Blood glucose values should be within a normal range (48 mmol/mol) in order for people with diabetes to minimize the risk of future complications.

This chapter describes what normal blood sugar levels are among adults and children with type 1 diabetes and type 2 diabetes.

Individuals with diabetes who measure blood sugar daily at home need to know how they interpret sugar levels to adjust meals, activities and medicines.

It is difficult to specify normal or optimal blood sugar levels for all people because target values need to be adapted for each individual. People without diabetes have long-term blood sugar (HbA1c) 42 mmol/mol, despite this, it is believed that optimal levels for people with diabetes are HbA1c 48 mmol/mol.

Recommended blood sugar levels

The recommended blood sugar levels are listed below for adults with type 1 diabetes, type 2 diabetes and children with type 1 diabetes.

The table provides general guidance. An individual goal set by your healthcare team is what you should strive for.

Recommended levels from the organization NICE

Type of diabetesIn the morningBefore meals (pre-prandial)Approximately 90 minutes after meals (post-prandial)
Non -diabetic4.0 to 5.9 mmol/l< 7.8 mmol/l
Type 2 diabetes4 to 7 mmol/l< 8.5 mmol/l
Type 1 diabetes5 – 7 mmol/l4 to 7 mmol/l5 to 9 mmol/l
Children with type 1 diabetes4 – 7 mmol/l4 to 7 mmol/l5 to 9 mmol/l

*Figures for non-diabetics are provided for information but are not included in Nice guidelines.

Normal blood sugar in diabetes mellitus

For most healthy individuals, normal blood sugar levels are as follows:

  • Between 4.0 to 5.4 mmol/l (72 to 99 mg/dl) on fasting
  • Up to 7.8 mmol/l (140 mg/dl) 2 hours after eating

For people with diabetes, target blood sugar values are as follows:

  • Before meals: 4 to 7 mmol/l for people with type 1 or type 2 diabetes
  • After meals: below 9 mmol/l for people with type 1 diabetes and below 8.5 mmol/l for people with type 2 diabetes

Blood sugar levels in the diagnosis of diabetesThe following table contains criteria for diagnosing diabetes and prediabetes.

Blood sugar levels in diabetes and prediabetes

Random measure< 11.1 mmol/l> 11.1 mmol/l
Fasting< 5.5 mmol/l5.5 – 6.9 mmol/l> 7.0 mmol/l or
2h after meal< 7.8 mmol/l7.8 – 11.0 mmol/l> 11.1 mmol/l

Fasting glucose in the blood

A fasting plasma glucose sample is taken after at least eight hours of fasting and is therefore usually taken in the morning.

In NICE guidelines, fasting plasma glucose of 5.5 to 6.9 mmol/l is considered to be at greater risk of developing type 2 diabetes, especially when accompanied by other risk factors for type 2 diabetes.

Oral Glucose Tolerance Test (OGTT)

An oral glucose tolerance test involves taking a fasting sample of blood and then drinking a very sweet drink containing 75 g of glucose.

After drinking this drink, you need to rest until further blood tests are taken after 2 hours.

HbA1c for the diagnosis of diabetes

An HbA1c test does not measure blood glucose levels directly, but the result of the test is influenced by how high or low blood sugar levels have been in the last 2 to 3 months.

HbA1c in diabetes or prediabetes

  • Normal: below 42 mmol/mol
  • Prediabetes: 42 to 47 mmol/mol
  • Diabetes: 48 mmol/mol

Why is good blood sugar levels important?

It is important that you control your blood sugar levels as well as you can because high sugar levels over long periods increase the risk of diabetic complications.

Examples of diabetes-related complications

  • Kidney Disease
  • Nerve injury
  • Disease of the retina
  • Heart disease
  • Stroke

This list of complications may look frightening, but the main thing to remember is that the risk of these problems can be minimized by good blood sugar control.

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