What Are Normal Blood Sugar Levels?

Written by
The Manual Team
Medically approved by
Dr Earim Chaudry
Last updated
7th January 2022

In 30 Seconds… 

Your blood sugar levels measure the amount of glucose (sugar) you have in your bloodstream at any given time.

These levels go up and down throughout the day, and for people living with diabetes, significant changes in blood sugar levels require careful monitoring. 

Upon waking or before eating, the average blood sugar level for non-diabetics is around 5.6 mmol/L (100 mg/dL).

Whether you have diabetes (type 1 or type 2), you’re prediabetic, or you’re trying to lose weight and improve your health, understanding your blood sugar is vitally important.   

In this article, we explain what your blood sugar levels are, what normal blood sugar levels look like, and why they matter to your health and well-being. 

What Are Blood Sugar Levels?

When you consume food and drink throughout the day, your stomach breaks down and absorbs the glucose (sugar) present into your bloodstream. 

Although eating too much “free” sugar (chocolate, sweets, fizzy drinks) is bad for your health, it’s important to remember that natural sugar is a key energy source which is required for the proper function of muscles, organs, and cells. Common sources of this type of glucose include carbohydrates, such as fruit, pasta, bread, and cereals.

Your blood sugar levels, therefore, are a measurement of how much glucose you have in your blood at any given time. These levels fluctuate throughout the day, and for people living with diabetes, changes in blood sugar levels are more frequent and pronounced — and require careful monitoring. 

So, What Are Normal Blood Sugar Levels?

In the UK, glucose levels are measured following the international standard, which measures the molarity (i.e., the number of molecules of a substance within a specific volume). This is displayed as mmol/L (millimoles per litre). 

Other countries, like the US and Germany, measure in mg/dL (milligrams per decilitre).

  • Normal blood sugar levels in non-diabetics — when you first wake up or before eating — range from between 3.9 and 7.1 mmol/L (70 to 130 mg/dL). The average blood sugar level is around 5.6 mmol/L (100 mg/dL). This is known as your fasting blood sugar level
  • A few hours after eating, your blood glucose level may temporarily rise to around 7.8 mmol/L (140 mg/dL).
  • In diabetics, a healthy target range for blood glucose should be between 5.0 and 7.2 mmol/L (90 to 130 mg/dL) before eating, and less than 10 mmol/L (180 mg/dL) a few hours after eating.

Why Do Your Blood Sugar Levels Matter? 

In order for your cells to function properly, they require energy, and healthy, natural sugars found in fruit (fructose) and in dairy products (lactose) help to provide that energy.

Once absorbed into your bloodstream, sugar enters your cells thanks to a hormone called insulin (produced by your pancreas), but if you don’t have enough insulin, the sugar stays put in your blood, building up over time. 

Prolonged, uncontrolled high blood sugar levels can result in:

  • Damage to your blood vessels 
  • High blood pressure
  • Kidney disease
  • Coronary heart disease
  • Nerve damage
  • Vision problems

High blood sugar levels can also point to you either having diabetes or being at a high risk of developing diabetes. Symptoms of diabetes can include frequent urination, increased thirst, weight loss, tiredness, blurred vision, and recurring infections, but a blood sugar test will offer a clear diagnosis.

Keeping your blood sugar levels within a normal range is, therefore, a crucial part of managing your weight and avoiding serious long-term health issues.

Failing to do so can lead to your blood sugar levels getting too high (hyperglycemia) or too low (hypoglycemia), which can result in a whole host of complications. 

What is Hyperglycemia?

The medical term for a high blood sugar level is Hyperglycemia.

It typically affects people with type 1 diabetes (where the body attacks the cells in the pancreas, meaning it cannot make any insulin) and type 2 diabetes (where the body is unable to make enough insulin, or the insulin doesn’t work properly).

However, it can also impact non-diabetics, especially those who have recently suffered a heart attack or stroke. 

Symptoms of hyperglycemia can include:

  • Frequent urination
  • Dry mouth or increased thirst
  • Fatigue
  • Blurred vision
  • Stomach pain
  • Nausea or vomiting
  • Unintentional weight loss
  • Recurring infections (such as skin or bladder infections)
  • A fruity odour to the breath

If you’re experiencing any of these symptoms, it could be time for a diabetes test. Speak with your GP or healthcare provider.

What is Hypoglycemia?

The prefix “hyper” comes from the Greek, meaning “over.” “Hypo” is the opposite, meaning “under.”

Hypoglycemia is, therefore, the medical term for low blood sugar, where the level of glucose in your bloodstream drops to 4 mmol/lor or below.

It mainly impacts those with diabetes, and you may have heard it described as “having a hypo.”

Symptoms of low blood sugar levels vary from one person to the next, but they typically include:

  • Tiredness
  • Dizziness
  • Sweating
  • Turning pale
  • Hunger
  • Trembling
  • Heart palpitations
  • Tingling lips
  • Feelings of irritability, anger, or anxiety

If left untreated, symptoms can progress to:

  • Blurred vision
  • Weakness
  • Confusion
  • Slurred speech
  • Clumsiness
  • Fatigue
  • Weakness
  • Passing out
  • Fits or seizures

A hypo can happen at any time, even when you’re asleep. If not treated quickly, a low blood sugar level can be dangerous, but it can usually be treated quickly by eating or drinking fast-acting carbohydrates. Think sugary foods without fat or protein, so that they’re more easily converted into sugar in your body. Fruit juice, honey, regular soft drinks, or sugary sweets often do the trick.

Are You At Risk of Developing Diabetes?

Beyond diet and lifestyle — namely being overweight or having high blood pressure — there are a few inherent risk factors associated with type 2 diabetes that you need to be aware of. These include:

  • Being male
  • Being over the age of 40
  • Being of Chinese, South Asian, African-Caribbean, or black African background
  • Having a close relative with diabetes

If more than one of those applies, you’re at greater risk of developing diabetes. 

Diabetes UK has a handy online tool to check your own situation against these factors. Before you start, you’ll need to know your height, weight, and waist measurements.

Blood Glucose Test, Diabetes Treatment, and Lifestyle Changes

If you’re experiencing any of the health problems, medical conditions, or diabetes symptoms described in this article, then it could be time for a blood glucose test. This will involve your healthcare provider taking a urine sample and/or a blood sample to check your blood sugar levels.

If your test results confirm a diabetes diagnosis, your GP will discuss with you how it will impact your life and outline a treatment plan. 

This will typically involve:

  • Medical advice, including the possibility of taking diabetes medication;
  • The development of a physical activity and meal plan to encourage weight loss;
  • How your lifestyle will need to change (i.e., if you smoke or drink alcohol);
  • How you will monitor your blood sugar levels (often via a finger-prick test, where a drop of blood is added to a test strip and your glucose levels are monitored using a glucose meter or monitor);
  • And an explanation of the A1C test (also called an HBA1C) which measures your average blood sugar levels over 2-3 months. Everyone with diabetes is entitled to this test.
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Key Takeaways

Understanding the importance of your blood sugar levels can go a long way towards protecting yourself from diabetes complications now and later in life. 

If you find yourself in one or more of those risk categories, you’re eating all the wrong stuff, or if your trousers are simply feeling a little tighter, act now and embrace a healthier lifestyle before it’s too late.

Get inspired: Check out our Daily Health articles for diet and lifestyle tips and advice.


  1. nhs.com- Sugar: the factsEat well: https://www.nhs.uk/live-well/eat-well/how-does-sugar-in-our-diet-affect-our-health/


  2. www.healthline.com -Everything You Need to Know About Glucose: https://www.healthline.com/health/glucose

  3. Blood Sugar Converter –https://www.diabetes.co.uk/blood-sugar-converter.html

  4. Mayoclinc.org- Hyperglycemia in diabetes: https://www.mayoclinic.org/diseases-conditions/hyperglycemia/symptoms-causes/syc-20373631

  5. Maybe- Hypoglycemia: https://www.mayoclinic.org/diseases-conditions/hypoglycemia/diagnosis-treatment/drc-20373689

  6. riskscore.diabetes.org.uk- Find out your risk of Type 2 diabetes: https://riskscore.diabetes.org.uk/start

  7. Checking your blood sugar levels- https://www.diabetes.org.uk/guide-to-diabetes/managing-your-diabetes/testing

  8. diabetes.org.uk – What is hba1c?: https://www.diabetes.org.uk/guide-to-diabetes/managing-your-diabetes/hba1c

While we've ensured that everything you read on the Health Centre is medically reviewed and approved, information presented here is not intended to be a substitute for professional medical advice, diagnosis, or treatment. It should never be relied upon for specific medical advice. If you have any questions or concerns, please talk to your doctor.

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