Author – Phoebe Chan – BSc (Hons) Nutrition and Human Health
What Are Blood Sugar Levels?
We all need glucose in our blood to provide our cells with energy. Glucose comes from the food and drinks we consume. After we eat, a hormone called insulin briefly rises in the body. Insulin helps the body absorb glucose from the blood, so it can be used as energy. Your blood sugar levels, also known as blood glucose levels, are the amount of glucose in your blood. While the amount can go up or down throughout the day, there is a blood test called HbA1c that can measure your average blood sugar levels over about 3 months (1).
Why Are Blood Sugar Levels Important?
If the body doesn’t receive enough insulin to control the sugar from food and drink, the sugar stays in the bloodstream. This can also happen if you have insulin resistance, which means the body does not respond to insulin properly. Over time, high blood pressure can damage blood vessels, leading to health problems such as coronary heart disease, kidney disease and diabetic eye disease (1).
What Are Normal Blood Sugar Levels?
For most healthy individuals, normal blood levels are:
| When fasting | 2 hours after eating |
| Between 4.0 to 5.4 mmol/L | up to 7.8 mmol/L |
For people with diabetes, blood sugar level targets are as follows:
| Type of diabetes | Before meals | After meals |
| Type 1 diabetes | 4 to 7 mmol/L | Under 9 mmol/L |
| Type 2 diabetes | 4 to 7 mmol/L | Under 8.5 mmol/L |
The Dangers of High Blood Sugar
Eating a diet high in sugar can lead to insulin resistance, meaning the body stops responding properly to the effects of insulin.
Slightly elevated blood sugar is known as prediabetes. According to the Centres for Disease Control and Prevention (CDC), more than 80% of people with prediabetes don’t know they have it and often don’t realise until they go on develop type 2 diabetes. These individuals may experience symptoms such as blurry vision, extreme thirst and hunger, skin changes, tingling in hands or feet, unexpected weight loss and urinating often.
High blood sugar can be managed and supervised by a healthcare provider. However, if left unmanaged, it can lead to serious health issues such as heart disease, eye issues and kidney problems (2).
How to Manage High Blood Sugar Levels
Sticking to healthy habits can lower blood sugar levels and also prevent your diabetes risk, even if you have a family history of the condition.
Eating a Well-Balanced Diet
If you have diabetes, it is important to include a wide variety of nutritious and healthy foods in your diet and avoid snacking on sugary foods (2).
There’s also evidence to show that the Mediterranean-style diet can promote weight loss and improve blood glucose management in people with type 2 diabetes. This is a diet based on plant foods, therefore includes a lot of fruits and vegetables, beans and pulses, nuts and seeds and wholegrains. It also includes some dairy and lean protein such as chicken, eggs and fish (3).
Eating a lot of salt can also increase your risk of high blood pressure, which is why limiting salt intake is important to minimise complications. Cooking from scratch is highly recommended as lots of pre-packaged foods already contain salt. Herbs and spices can be swapped out for salt to add extra flavour (5).
Exercise
Regular exercise can help keep your blood sugar in your target range as it helps the body use insulin (2). If you’re unable to do physical activity such as walking, swimming or gym work, you could consider water aerobics, chair exercises or strength resistance training with light weight (4).
Quit smoking
Smoking is the greatest single lifestyle factor for developing diabetes complications. It can outweigh all the benefits gained by weight loss, healthy eating, good blood glucose and blood pressure control.
Smoking affects circulation by increasing heart rate and blood pressure, and by making small blood vessels narrower. Smoking can also make the blood cells and blood vessel walls sticky and lets dangerous fatty material to build up. Consequently, this can lead to heart attack, stroke and other blood vessel diseases. People with diabetes who smoke have higher blood glucose levels and less control over their diabetes than non-smokers with diabetes (4).
The Dangers of Low Blood Sugar Levels
Low blood sugar, or hypoglycaemia, is usually where your blood glucose is below 4 mmol/L. it usually effects people with diabetes who take insulin or other diabetes medications. Symptoms include feeling hungry, feeling dizzy, feeling anxious, sweating, shaking, changes in vision and feeling confused (6).
It is common for diabetes to cause hyperglycaemia, however medicines to lower blood sugar can sometimes make it go too low. This is common if you take insulin or other diabetes medicine such gliclazide and glimepiride. You’re more likely to get low blood sugar if you take too much insulin, have problems with the way you inject insulin, miss or delay meals, do a lot of exercise or drink a lot of alcohol (6).
Treatment of Low Blood Sugar
If you have hypoglycaemia symptoms, it is recommended to do the following:
- Eat or drink 15-20 g of fast-acting carbohydrates: these are sugary foods or drinks without protein or fat that are easily converted to sugar in the body. Glucose tablets, fruit juice, soda, or sugary candy may be beneficial.
- Recheck blood sugar levels 15 minutes after treatment: if blood sugar levels are still under 70 mg/dL (3.9 mmol/L), eat or drink another 15-20 g of fast-acting carbohydrate, and recheck your blood sugar level again in 15 minutes. Repeat these steps until the blood sugar is above 70 mg/dL (3.9 mmol/L).
- Have a snack or meal: once blood sugar levels are back to the standard range, eating a healthy snack or meal can help prevent another drop in blood sugar and replenish the body’s glycogen stores (7).
Frequently Asked Question’s (FAQ’s)
What is blood sugar?
Blood sugar, or blood glucose, is the main type of sugar found in your blood. It comes from the food you eat and is your body’s primary source of energy. Your body uses insulin—a hormone made by the pancreas—to help move glucose from your blood into your cells for energy.
Why is it important to keep blood sugar normal?
Stable blood sugar helps maintain steady energy and mood while reducing long-term risks of diabetes, heart disease, and nerve or kidney problems.
What happens when blood sugar is too high?
High blood sugar (hyperglycaemia) can cause thirst, fatigue, and blurred vision. Over time, it may lead to insulin resistance and type 2 diabetes if not managed.
What happens when blood sugar is too low?
Low blood sugar (hypoglycaemia) can cause shakiness, dizziness, hunger, and confusion. It often happens when you skip meals or take too much insulin.
References
- https://www.bhf.org.uk/informationsupport/heart-matters-magazine/medical/tests/blood-sugar#:~:text=Mark%20Kearney%2C%20BHF%20Professor%20of,17%20December%202024
- https://www.optum.com/en/health-articles.html/healthy-living/what-normal-blood-sugar-level-and-why-does-it-matter
- https://www.diabetes.org.uk/living-with-diabetes/eating/meal-plans/mediterranean
- https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/diabetes-long-term-effects
- https://www.diabetes.org.uk/living-with-diabetes/eating/10-ways-to-eat-well-with-diabetes
- https://www.nhs.uk/conditions/low-blood-sugar-hypoglycaemia/
- https://www.mayoclinic.org/diseases-conditions/hypoglycemia/diagnosis-treatment/drc-20373689
