Blood sugar, or blood glucose, refers to the sugar (glucose) that is found in the blood and is the body’s main source of energy. Whenever we eat, the body converts food into glucose (sugar). With the help of insulin that's released from the pancreas, the glucose is absorbed into the bloodstream and used as energy.


The type of food we eat, as well as the amount of food, affects your blood sugar levels.

Below, find out everything you need to know about blood sugar. Next, check out some of our favourite high-protein lunches and high-protein snacks, as well as how much fibre should I eat in a day? And what is a low GI diet?

Blood sugar monitor

What are blood sugar levels?

Blood sugar levels, or blood glucose levels, is the term used when measuring the amount of sugar in the blood at any given time.

Different foods get broken down into glucose at different rates. For example, refined or simple carbohydrates such as crisps will be broken down and absorbed into the bloodstream a lot quicker than a complex carbohydrate such as rye bread. This is because complex carbohydrates contain longer chains of sugar molecules than simple carbohydrates, thereby taking longer for the body to breakdown into glucose. The faster the rate of absorption of sugar into the blood stream, the more likely this will cause a spike in your blood sugar levels. This is also referred to as ‘high blood sugar’.

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The body’s ability to break down food into glucose also relies on insulin, a hormone secreted by the pancreas when we eat that allows the glucose to enter the body’s cells and be used for energy. When the body cannot produce enough insulin, this leaves excess glucose or sugar in the blood stream because it is not being moved into the cells to be used for energy.

So, what does this mean?

· Type 1 diabetes – this is when the pancreas makes very little or no insulin.
· Type 2 diabetes – any insulin produced is less effective, also known as insulin resistance, or the body cannot make enough insulin to cope with the consistently high blood sugar levels.

For most of us, our body manages our blood sugar levels pretty well without us having to worry about it. However, if you do have high or low blood sugar levels this may affect how you feel physically and mentally, and can affect your weight, energy levels and moods.

Overtime, high blood sugar levels increase your risk of conditions such as type 2 diabetes, heart disease and dementia.

Factors that increase the risk of high blood sugars include:

· Too much sugar or refined carbohydrates in the diet
· Diets that are too low in protein or fats
· Lack of exercise
· Medications such as steroids and antidepressants
· Alcohol
· Caffeine
· Stress
· Smoking
· Dehydration
· Illness or surgery
· Pregnancy (gestational diabetes)

Low blood sugar is when blood sugar levels drop too low. This may be due to:

· Not eating enough in the day or skipping meals
· Too much exercise
· Hormone imbalance

Woman with diabetes pricking finger for test

What are normal blood sugar levels?

Normal blood sugar levels should be:

· between 4-5.7mmol/L before eating
· between 5 mmol/L and 9 mmol/L at least 90 minutes hours after eating

Your GP can check your blood sugar levels through a blood test and the standard marker is an HbA1c test. This is a non-fasting blood test that looks at your average blood sugar levels for the last two to three months.

If you have diabetes or your GP thinks you may be diabetic, they may then order additional tests such as a fasting blood glucose test, or a glucose tolerance test (GTT) which is more commonly done during pregnancy to rule out gestational diabetes.

What level of blood sugar is dangerous?

Blood sugar levels can become dangerous if they are constantly elevated, as the increased sugar in the blood can begin to damage internal organs. The higher your blood sugar levels and the longer they are higher, the more at risk you are.

High blood sugar symptoms

Hyperglycaemia, high blood sugar, is more common in those with diabetes, but it can also affect those who are not diabetic. In ether situation, persistently high blood sugar levels can be serious, and even life-threatening, if left untreated.

· Pre-meal or fasting blood sugar levels are greater than 7.0 mmol/L
· At least 90-minutes after eating blood sugar levels are greater than 11.0 mmol/L

Symptoms of hyperglycaemia include:

· Feeling very thirsty
· Increased urination
· Feeling weak or tired
· Blurred vision
· Weight loss

The best course of action if you struggle with high sugar levels is prevention:

· Avoid eating too much sugary or starchy foods
· Add more protein and good fats into your diet
· Find ways to manage your stress
· Regular exercise
· Healthy weight loss if you are overweight

If you are diabetic, take your diabetic medicine regularly and don’t change or skip the dose without consulting your GP first.

Woman with headache feeling faint

Low blood sugar symptoms

Low blood sugar is also known as hypoglycaemia. This is the opposite of hyperglycaemia, where blood sugar levels drop and your cells don’t get enough energy for your body to function. Low blood sugar levels are common in those with diabetes, especially if medication or a meal has been skipped, but it can also occur in those who are not diabetic.

Symptoms of hypoglycaemia include:

· Dizziness or feeling faint
· Feeling hungry
· Sweating
· Feeling tired or shaky
· Palpitations
· Tingling lips
· Turning pale
· Feeling anxious, irritable or more tearful

Hypoglycaemia can also be triggered by malnutrition, perhaps through an eating disorder like anorexia nervosa or illness, binge drinking, or certain conditions such as Addison’s disease.

If you feel that you may have low blood sugar levels:

· Have a sugary drink or snack, such as a fruit juice, a banana or a biscuit.
· If you haven’t eaten for a while, have something to eat that contains both protein and a slow-releasing carbohydrate such as, a piece of fruit with a handful of nuts, crispbreads with cheese or eggs on toast. You don’t want carbohydrates on their own as this may cause your blood sugars to spike.

What are blood sugar monitors?

Blood sugar monitors are a way to check your blood sugar yourself. They are devices that analyse your blood, usually through a finger prick, and can give you a blood glucose reading in the moment. Those with diabetes who use insulin should have one already to track blood sugar levels.

There are two main types of blood glucose monitors include:

· Instant blood glucose test strips – you prick your finger using a lancet, collect a blood spot using a test strip, and then insert the strip into a machine to get your blood glucose reading

· Continuous glucose monitor (CGM) or flash monitor – a small sensor is attached to your arm or tummy, that senses how much glucose is in the fluid under your skin. A reader or app on your phone then tracks the results of your blood glucose throughout the day and before or after meals.

There are then other options that include wearable tech devices such as certain smart watches or handheld devices that include USBs so you can upload results to your computer.

If you have diabetes, then it is a good idea to monitor your blood glucose levels under the recommendations of your diabetes care team or GP.

If you don’t have diabetes, then most of us shouldn’t need to track our blood sugars if we are eating a balanced diet and not experiencing the symptoms associated with high or low blood sugar levels. Long-term use of blood glucose monitors may lead to dietary changes or omitting certain food groups like carbohydrates from the diet which may then have other effects on health and cause nutrient deficiencies. Blood glucose monitors are also not recommended for those who struggle with health anxiety or have a history of an eating disorder, as this may exacerbate symptoms.

If, however, you suspect that your blood sugars are often too high or too low, using a blood glucose monitor may be beneficial in the short term (e.g. 2-4 weeks) to help you identify patterns or certain foods that may be making them better or worse. It is recommended that you do this alongside your GP or a registered nutritionist or dietician to ensure that you are reading the information accurately and can get the right support.

What is the blood sugar diet?

The blood sugar diet was created specifically to help those who are overweight and have high blood sugar levels. It focuses on a low calorie (800 calories a day), low carbohydrate, Mediterranean-style diet, with more movement to help improve blood sugar regulation. It is designed to promote rapid weight loss in the first 12 weeks before you move into a reintroduction phase. You must speak to your doctor first before trying this diet, especially if you have a pre-existing medical condition or are on medication.

Low carbohydrate diets, like the blood sugar diet, focus on reducing refined and simple carbohydrates that can cause spikes in blood sugar levels. Similarly, a low-GI (glycaemic index) diet is also based on blood sugars. It ranks carbohydrates from 0-100 based on the rate at which the energy they provide is broken down by the body into sugar (glucose). Read more in our guide: what is a low-GI diet?

By slowing down the rate and volume at which your body releases sugar into the blood, it helps to maintain more balanced blood sugar levels.

Recipes to help balance blood sugar

Spicy meatballs with chilli black beans
High-protein breakfast
Chicken satay salad
Pepper, tomato & ham omelette
Baked salmon & leek parcel
Avocado & black bean eggs

In summary...

Balancing your blood sugars is important when it comes to your health not only in preventing the risk of obesity, diabetes and heart disease, but if you already have type 2 diabetes then you may be able to put it into remission. Reducing sugar and starchy carbohydrates in your diet as well as moving more in your day are some of the first steps you can take, but if you are concerned about your blood sugar levels then please speak to your GP.

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Nicola Shubrook is a nutritional therapist and works with both private clients and the corporate sector. She is an accredited member of the British Association for Nutrition and Lifestyle Medicine (BANT) and the Complementary & Natural Healthcare Council (CNHC). Find out more at


All health content on is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact your local health care provider. See our website terms and conditions for more information.

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