All about blood sugar levels 

Written by

Lauren Dobischok
14 March, 2023

Medically checked article All HOMED-IQ content is reviewed by medical specialists

Blood sugar, or glucose, is the main sugar found in the blood of humans and other animals. Glucose comes from the food we eat and is an important source of energy for our bodies. Maintaining a normal blood sugar level is important for good health, but certain lifestyle habits and diseases can cause blood sugar to be either too high or too low. In this article we will go into more detail about what exactly blood sugar levels are, how they are measured, and why it is important to keep an eye on them. We also discuss normal blood sugar levels and what steps to take if your blood sugar is outside the healthy range. Read on to learn more about blood sugar levels and how to regulate them.

What are blood sugar levels?

Blood sugar levels are the concentration of glucose (sugar) in the blood. Your blood sugar level changes throughout the day depending on what you eat and drink. As glucose is the body’s main source of energy, humans require a minimum blood sugar level to function normally. Conversely, too much sugar in the blood can damage blood vessels over time, causing health problems such as diabetes, kidney disease, or heart disease (CDC, 2022). 

Who needs to measure their blood sugar level? 

People with diabetes 

If you have diabetes, it is important to regularly measure your blood sugar to ensure it is well managed. Diabetes is a condition in which there is too much glucose (sugar) in the blood. Diabetes occurs when the body does not produce insulin or is not able to use it properly (CDC, 2022). Insulin is a hormone that moves glucose in the blood into the body’s cells to produce energy. Without enough insulin or a resistance to it, glucose builds up in the blood, causing high blood sugar. There are two types of diabetes: type 1 and type 2. 

Type 1 diabetes: Type 1 diabetes is an autoimmune condition in which the body does not produce insulin. People with type 1 diabetes must take insulin for life to control their blood sugar, either via injections or an insulin pump. Type 1 diabetes usually develops at a young age, but can also be diagnosed in adults.

Type 2 diabetes: Type 2 diabetes occurs when the body does not produce enough insulin or does not use it properly. Unlike type 1 diabetes, it is possible to manage type 2 diabetes without insulin by lifestyle changes, such as weight loss, diet changes, and exercising more.

People without diabetes

Diabetes can develop gradually and people may not notice they have it until severe symptoms occur. Individuals that do not have diabetes but who may be at risk may check their blood sugar periodically to ensure it is in a healthy range (CDC, 2022). Risk factors for type 2 diabetes include:

  • Being overweight
  • Having prediabetes
  • Being older than 45
  • Having a parent or sibling with type 2 diabetes
  • Having had gestational diabetes
  • Not being physically active
  • Being from certain ethnicities, including: Black, Turkish, South Asian, or Moroccan. Certain ethnicities are at higher risk of developing type 2 diabetes at a younger age.

Source: Thuisarts, 2021, CDC, 2022

While type 1 diabetes cannot be prevented, type 2 diabetes can be avoided by detecting slightly elevated blood sugar and making lifestyle changes before diabetes occurs (pre-diabetes). Measuring blood sugar in non-diabetics can also help diagnose diabetes that hasn’t caused noticeable symptoms and allow treatment to begin before complications occur.

How do you measure blood sugar levels?

There are several types of blood sugar tests that can be used to diagnose or monitor diabetes. It is important for people with diabetes to measure their blood sugar level regularly to ensure their diabetes is well controlled.

Self-testing blood sugar 

People with diabetes may need to check their blood sugar several times throughout the day, depending on the type of diabetes they have and their treatment plan. Self-testing blood sugar helps people with diabetes understand how their bodies respond to food, exercise, and medication, and ensure their blood sugar stays in a healthy range. Blood sugar monitoring can be done using a blood sugar meter, which measures the sugar level in a small amount of blood, usually from the fingertip. A continuous glucose monitor (CGM) can also be used to measure blood sugar. CGMs are a device worn on the skin that can continuously monitor blood sugar levels without needing to prick your finger (CDC, 2022). 

Fasting blood sugar test

A fasting blood sugar test can be used to diagnose diabetes and is performed after not eating or drinking (except water) for 8-12 hours, usually overnight (Cleveland Clinic, 2021). This test is performed by a healthcare provider and involves taking a blood sample from the fingertip or vein. A fasting blood sugar level of 7.0 mmol/l (126 ng/dl) or more indicates diabetes. A level between 6.1 and 6.9 mmol/l indicates pre-diabetes (Mayo Clinic, 2022). 

Glucose Tolerance Test

A glucose tolerance test measures blood sugar levels before and after drinking a liquid that contains glucose. This test can be used to diagnose diabetes or gestational diabetes (diabetes during pregnancy). The test involves measuring blood sugar when fasting (not having eaten or drank anything other than water for 8-12 hours) followed by measuring blood sugar 1, 2, or 3 hours after drinking the glucose liquid (Mayo Clinic, 2023). The blood sugar that indicates diabetes with this test depends on when the measurement is taken and whether you are pregnant or not. 

Random Blood Sugar Test (Non-fasted blood sugar)

This test measures your blood sugar at the moment you are tested and can be used to diagnose diabetes. You do not need to fast (not eat) before this test. A non-fasted blood sugar level above 11 mmol/l (200 ng/dl) indicates diabetes (Mayo Clinic, 2023).

HbA1c Test 

An HbA1c test measures your average blood sugar level over the past 2-3 months. This test can be used to diagnose and monitor people with diabetes. HbA1c stands for glycated hemoglobin, or hemoglobin coated in glucose. HbA1c is produced when glucose attaches to the red blood cells in your body. The more glucose in your blood, the more HbA1c is produced.

Since red blood cells have a lifespan of approximately 3 months and are constantly renewing in the body, the test result will indicate whether your average blood glucose value over the past ~3 months is within or outside the reference values. An HbA1c level above 7.0% may indicate diabetes. For people with diabetes, a target HbA1c is usually around 7%, but may depend on other factors such as age. Your doctor will help you set a personal HbA1c goal (CDC, 2022). 

It is possible to check your HbA1c level from home using Homed-IQ’s Blood Sugar Test. This blood test involves taking a finger prick blood sample and mailing it to a laboratory for analysis. 

At what blood sugar level do you have diabetes? 

The blood sugar level that indicates diabetes depends on the type of test that is used. A fasting blood sugar level of 7 mmol/l (126 ng/dl) or higher, or a random blood sugar level of 11.1 mmol/l (200 ng/dl) or higher may indicate diabetes. An HbA1c level above 7% can also indicate diabetes. 

It usually requires more than one test to diagnose diabetes. Do you suspect you have diabetes? See your doctor for further advice and testing.

What is mmol/l and ng/ml?

Mmol/l stands for millimoles per liter and is a unit for the concentration of substances in an amount of fluid. Depending on the country, mmol/l or mg/dl (milligrams per deciliter) are used to express blood sugar measurements. For example, a blood sugar value of 5 mmol/l means that there is 5 millimoles of glucose (sugar) per liter of blood, or 90 milligrams per deciliter of blood.

What is a healthy blood sugar level?

A healthy blood sugar level (for a non-diabetic person) is generally less than 5.6 mmol/l after fasting and below 7.8 mmol/l 1.5 to 2 hours after a meal (Mayo Clinic, 2022). The cut-off points for diagnosing diabetes can vary and test results must be interpreted by a doctor. A high blood sugar level (hyperglycemia) may indicate diabetes. 

What should you do if you have high blood sugar? 

If you have diabetes, it is important to keep your blood sugar level from getting too high. Be sure to:

  • Speak with your doctor: Your doctor can provide advice on how to manage your blood sugar over time and adjust your insulin dose as needed.
  • Check your blood sugar: Monitor your blood sugar regularly and discuss any changes with your doctor.
  • Take diabetes medication as directed: Be sure to take medication as directed by your doctor or care team. 
  • Drink non-sugary liquids: Dehydration can cause high blood sugar.
  • Control the amount of sugary or starchy foods you eat: These foods are high in carbohydrates and can cause rapid spikes in blood sugar.
  • Exercise regularly: Try to incorporate light physical activity into you routine every day, such as walking, bike riding, or swimming.

Source: NHS, 2023

It is important to remember that high blood sugar over a long period of time can cause damage to organs and tissues. If your blood sugar is high it is important to speak to your doctor on how best to manage your levels. While some people can control their blood sugar with lifestyle changes like diet and exercise, others require medication to maintain a healthy blood sugar level.

What should you do if you have low blood sugar? 

Low blood sugar or hypoglycemia occurs when your blood sugar level drops too low. It mainly affects people with diabetes who take insulin. Low blood sugar can be dangerous and it is important to take immediate action to raise it. Below are some steps you can take:

  • Eat or drink fast-acting carbs: Fast-acting carbohydrates include sugar, honey, glucose tablets, juice, candy, or non-diet soda.
  • Monitor blood sugar: Monitor your blood sugar 10 minutes after consuming the fast-acting carbs. If there is no change, have more fast-acting carbs and measure again after 10-15 minutes.
  • Have a snack or meal: Once your blood sugar is back in the normal range, you may need to have a meal or snack containing slow-release carbs (such as a slice of bread or crackers with cheese) to prevent another drop in blood sugar. 
  • Speak with your doctor: If you have had severely low blood sugar or several episodes of low blood sugar close together, speak to your doctor. They may need to make changes in your diabetes care plan.

Source: NHS, 2020

How can you manage your blood sugar levels?

Maintaining a normal blood sugar level is important for preventing type 2 diabetes and for ensuring people with diabetes stay healthy. Tips for managing your blood sugar include:

  • Follow a healthy and balanced diet, with plenty of vegetables, fruits, whole grain products and protein-rich foods
  • Maintain a healthy weight
  • Exercise regularly
  • Avoid stress
  • Measure blood sugar levels regularly
  • Eat at regular times and do not skip meals
  • Limit alcohol, juice, and soda

Source: CDC, 2022

If you have diabetes, it is important to work closely with your doctor to keep your blood sugar levels under control. This will help you avoid complications in the future and lead a healthy and active life.

In summary, blood sugar levels indicate how much glucose is present in the blood and are an important indicator of our health. Blood sugar can be measured in a variety of ways, and a blood sugar test can be used to diagnose diabetes or ensure diabetes is being managed. A healthy blood sugar level can be achieved through a healthy and balanced diet, regular exercise, regular blood sugar measurements, and using diabetes medication as prescribed. 

Interested in measuring your average blood sugar (HbA1c) from home? Try Homed-IQ’s Blood Sugar Test.


All About Your A1C. (2018, August 21). Centers for Disease Control and Prevention. https://www.cdc.gov/diabetes/managing/managing-blood-sugar/a1c.html

Diabetes – Diagnosis and treatment – Mayo Clinic. (2023, January 20). https://www.mayoclinic.org/diseases-conditions/diabetes/diagnosis-treatment/drc-20371451

Diabetes Risk Factors. (2022, April 5). Centers for Disease Control and Prevention. https://www.cdc.gov/diabetes/basics/risk-factors.html

Fasting Blood Sugar: Screening Test for Diabetes. (n.d.). Cleveland Clinic. https://my.clevelandclinic.org/health/diagnostics/21952-fasting-blood-sugar

Hyperglycaemia (high blood sugar). (2023). NHS Inform. https://www.nhsinform.scot/illnesses-and-conditions/blood-and-lymph/hyperglycaemia-high-blood-sugar#:~:text=drink%20plenty%20of%20sugar%2Dfree,about%20how%20to%20do%20this

Manage Blood Sugar. (2021, April 28). Centers for Disease Control and Prevention. https://www.cdc.gov/diabetes/managing/manage-blood-sugar.html

Monitoring Your Blood Sugar. (2022, January 28). Centers for Disease Control and Prevention. https://www.cdc.gov/diabetes/managing/managing-blood-sugar/bloodglucosemonitoring.html

Prediabetes – Diagnosis and treatment – Mayo Clinic. (2022, November 19). https://www.mayoclinic.org/diseases-conditions/prediabetes/diagnosis-treatment/drc-20355284

Prevent Diabetes Complications. (2022, November 3). Centers for Disease Control and Prevention. https://www.cdc.gov/diabetes/managing/problems.html

Thuisarts. (2021, November 22). Ik heb een verhoogde kans op diabetes type 2. Thuiarts. https://www.thuisarts.nl/diabetes-type-2/ik-heb-verhoogde-kans-op-diabetes-type-2

Website, N. (2022, September 16). Low blood sugar (hypoglycaemia). nhs.uk. https://www.nhs.uk/conditions/low-blood-sugar-hypoglycaemia/

What is Diabetes? (2022, July 7). Centers for Disease Control and Prevention. https://www.cdc.gov/diabetes/basics/diabetes.html#:~:text=With%20diabetes%2C%20your%20body%20doesn,vision%20loss%2C%20and%20kidney%20disease.

About the author

Lauren Dobischok

Lauren is a health scientist and science communicator currently living in the Netherlands. Originally from Canada, she completed a Research Master’s in Health Sciences at the Netherlands Institute of Health Sciences at Erasmus University Rotterdam (NIHES) with a specialisation in epidemiology. Prior to her master’s degree, she completed a Bachelor’s degree in Health Sciences at Simon Fraser University. With a background in public health, her goal is to create accurate scientific content that is easy to understand and empowers people to make informed decisions. Within Homed-IQ, Lauren works as a Product Developer and Content Lead, working closely with physicians and scientists on medical devices for Homed-IQ’s new products and written communications.