Symptoms of high and low blood sugar

Symptoms of high and low blood sugar

Managing your blood sugar levels is essential for your energy, brain function, mood and basic functions of your body. Our nutritionists explain the symptoms of high and low blood sugar, what normal levels of blood sugar should be, and how to manage your blood sugar healthily through your diet.

What are blood sugar levels?

Blood sugar levels are the measurement of glucose in your blood. Sugar and carbohydrates are consumed in the form of food and drinks and get broken down into glucose before entering the blood stream through the intestinal wall. The glucose in our blood is then carried into our body's cells for energy production.

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When blood sugar levels are tested, if they are showing as high (known as 'hyperglycemia'), this may indicate insulin resistance or diabetes. Learn more in our nutritionists article 'What is insulin resistance'.

If blood sugar levels are low, this is known as 'hypoglycemia' and can be caused by a number of things, including not eating regularly, not eating enough, an increase in physical activity without an increase in calories, and alcohol consumption.

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Are blood glucose and blood sugar levels the same thing?

Yes, blood sugar is another word for blood glucose. Sugars and carbohydrates in your food and drink are broken down in your gut and then enter the blood stream as glucose. You may also enjoy 'Why you should improve your gut health'.

What is a normal blood sugar level?

Normal blood glucose levels are from between 4.0 to 5.4 mmol (millimol) per litre of blood when fasting, and up to 7.8 mmol per litre of blood two hours after a meal.

If you're having your blood sugar levels tested, your doctor will perform something called a 'glucose tolerance test' which involves two blood tests, one after fasting, and one after the consumption of a sugary drink. 

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High blood sugar symptoms

Having high blood sugar can leave you with a few symptoms, however some people may not have any symptoms, so if you are concerned, get your blood sugar levels checked by your GP.

Urinating frequently 

As blood glucose levels rise, the body attempts to excrete some of it though the kidneys. This causes a higher volume of urine to be made, and an excessive need to urinate. Learn more about the importance of checking your urine in 'What colour should your urine be?'.

Excessive thirst

As the kidneys make more urine to excrete the excess blood glucose, you will need to drink more water to compensate for the loss.

Skin discolouration or skin tags

With an increase in insulin levels in the blood, there is an increase in a hormone called 'insulin-like growth factor', which triggers the growth of skin tags, and dark, velvety patches of skin, especially in the armpits, neck and groin.

Discover more articles on how to look after your skin here

Low blood sugar symptoms

As with high blood sugar symptoms, low blood sugar symptoms may not present themselves, however if they do it's likely to include these symptoms.


Tiredness may result if there is not enough glucose in the blood to get into the cells. Some people's body's adapt so that it can make energy out of fats via a process called 'ketosis', which can also be a warning sign of diabetes or a sign of diabetes getting out of control. The body can also make some glucose out of protein, in a lengthy biological process called 'gluconeogenesis'.


When your blood glucose levels are low, your brain tries to conserve energy which may leave you feeling light headed and dizzy.

Feeling hungry

Feeling hungry is a natural reaction to low blood glucose levels as the body tries to increase the levels of glucose in the blood. You may also be craving sweet or carbohydrate rich foods.

Shaking or trembling

Low blood glucose levels are stressful for the body. It triggers the release of the stress hormones, including cortisol, which may then cause tremors and shaking. Learn more in 'What is cortisol?' and 'Foods and vitamins to help relieve anxiety'.

Feeling irritable, anxious or moody

Feelings of anxiety, irritability or mood swings may come and go as a result of not enough insulin entering the brain. Insulin takes the happy hormone - serotonin - into the brain where it balances our mood and helps to relieve anxiety.  If your brain isn't receiving serotonin via insulin, it can leave you feeling irritable, anxious and moody. You might enjoy our nutritionists blog 'What supplements to take for brain health'.

How to lower blood sugar levels 

Eating a healthy balanced diet combined with exercise and following these tips is the best starting for lowering blood sugar levels.

Protein with complex carbohydrates

Complex carbohydrates include whole grains, whole-wheat bread, potatoes, quinoa, beans, oatmeal and many vegetables. They all provide healthy, slow releasing sugars. When you eat protein with complex carbohydrates, the protein slows down the release of the healthy sugars and helps limit the spike of blood sugar in your body. 

Discover the '5 best carbs for plant-based diets'.

Say 'No' to refined sugars

Refined sugars are just bad. Whether it's cookies, cakes, many pastas, sports drinks, many salad dressings, cereals, sauces, yogurts or sweeteners in foods and drinks, many of these foods include refined sugars which cause a spike in blood sugar and can lead to insulin resistance.

Cinnamon tea

Cinnamon has been studied for centuries and in particular in Ayurvedic and Chinese remedies to help maintain healthy blood sugar levels, normal blood sugar levels and stimulating your appetite. Cinnamon tea tastes great as it tastes sweet and hydrates you. 


Don't underestimate the power of water! Water is one of the best drinks for us - it has no calories, no sugar and often, when people think they're hungry they are actually thirsty. Before reaching for the snacks, have a glass of water, wait a few minutes and then check if you really need those snacks!

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Exercise is an essential part of lowering blood glucose levels. The body uses the excess glucose to power the body, ultimately lowering blood glucose levels.

How to increase blood sugar levels 

Eat every 2.5-3 hours

Eating regularly ensures a constant supply of glucose for the blood. Eat complex carbohydrates and protein as this combination ensures a steady release of glucose.

Avoid the highs and lows

Avoid sugar highs, as these highs then create sugar dips. Eat sensibly and frequently to ensure you are not peaking or dipping.

Eat healthy, calorie dense foods

Healthy, calorie-dense foods such as nut and seed butters, olives and avocados are excellent foods to go along with complex carbohydrates. These foods slow down your digestion, which helps to ensure a steady supply of glucose into the blood, preventing dips.

Choose different carbs before exercise

If you experience low blood sugar levels during exercise, you may need to take some additional sugars. You will need around 30g of sugar per hour of endurance exercise. This is equivalent to 1 cup of apple juice which is quick to enter the blood stream, providing pretty instant energy for your physical activity.

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