UK Edition
Blood sugar and glucose levels: what they mean, and what they should be
Your blood sugar level is in constant flux, depending on what you've eaten, when you ate it, and what you did afterwards. A finger-prick blood test can ascertain your level at any moment in the day – it's a crucial tool for diabetes sufferers, as they need to manage their body's insulin response.
In people with diabetes, explains Dr Soon Song, a consultant physician and diabetologist at BMI Thornbury Hospital in South Yorkshire and Sheffield Teaching Hospitals NHS Foundation Trust, the blood glucose levels are raised both before and after a meal.
“In a healthy individual without diabetes,” he says, “the body produces the correct amount of insulin from the pancreas to normalise the blood glucose level. But in diabetes, the pancreas does not produce enough insulin and/or the body is not able to use the glucose effectively due to lack of responsiveness to insulin action (known as insulin resistance).
“So the blood glucose level rises to abnormally high levels, which puts pressure on the body’s organs and nerves. causing permanent damage.”
What is blood sugar and glucose?
Sugar is a carbohydrate found naturally in food. There are different types of sugars: glucose belongs to a type of sugar called monosaccharides or simple sugar. It is the primary source of energy and the body tissues need glucose to function normally, especially the brain. “The terms blood sugar and blood glucose are often used interchangeably and refer to the amount of glucose carried in the blood,” says Dr Song.
What is a normal blood sugar level?
Understanding what is a normal blood sugar level is vital to diabetes prevention or management. Blood sugar level refers to the amount of glucose in the blood, sometimes known as blood glucose level; the concentration of glucose in the blood is expressed in mmol/l.
In healthy people without diabetes, your blood glucose level should measure between 4.0-5.5 mmol/l before a meal and should be less than 8.0 mmol/l two hours after a meal.
The blood glucose level is also measured by glycated haemoglobin, HbA1c, which gives information on the average blood glucose level over the last 2-3 months. A healthy person without diabetes should have HbA1c less than 42 mmol/mol.
Diabetes is diagnosed when the fasting blood glucose is greater than 7.0 mmol/l, random blood glucose greater than 11.1 mmol/l, or HbA1c greater than 48 mmol/mol.
A fasting blood glucose level between 5.5 and 6.9 mmol/l or HbA1c between 42 and 47 mmol/mol may indicate increased risk for type 2 diabetes, particularly those with obesity, family history of diabetes or from certain ethnic groups.
What are low blood sugar symptoms?
Low blood glucose is also known as hypoglycaemia. It is defined by blood glucose below 4 mmol/l.
“In the early stages of hypoglycaemia,” says Dr Song, “the body will react by releasing hormones such as adrenaline to warn that the blood glucose is going low so that actions can be taken to reverse the hypoglycaemia.
“This causes symptoms include palpitations, hunger, feeling warm or flushed, tremulous and sweaty.
“If the blood glucose falls lower, brain function will be affected resulting in confusion, irritability, aggressive behaviour, seizure and coma.
“Since the brain is highly dependent on glucose to function, frequent hypoglycaemia can cause cognitive impairment.”
Some people with diabetes may have hypoglycaemia unawareness where the warning symptoms are weak, especially during the early stages of hypoglycaemia. This usually occurs in those with long duration of diabetes, tight diabetes control or frequent hypoglycaemia. This condition is potentially dangerous as the patient is unaware the blood glucose is going low and therefore, not able to correct the low blood glucose at an early stage until it is too late when the brain function is affected. If untreated, prolonged severe hypoglycaemia can cause permanent brain damage.
People can experience hypoglycaemia at night when they're asleep. Low blood glucose level can wake the person up or lead to headaches, tiredness and sweat-soaked sheets in the morning.
What are the symptoms of high blood sugar?
The symptoms of high blood sugar level occur when diabetes is uncontrolled, regardless of the type of diabetes. Typically, the patient experiences thirst, dry mouth, frequent urination, blurred vision and tiredness. In more extreme cases, weight loss can occur.
Occasional mild periods of high blood sugar level are non-threatening. They can require treatment or return to normal levels on their own. But frequent or severe episodes can be dangerous and can lead to coma.
What happens if I don’t control my blood sugar?
Poorly controlled blood glucose levels can lead to health complications, warns Dr Song. “High glucose levels over a prolonged period, usually over several years, can damage the blood vessels in the eyes, kidneys, nerves and legs (peripheral vascular disease and gangrene). It can cause a heart attack or stroke. Apart from poor diabetes control, high blood pressure and high cholesterol levels also contribute to these complications. These risk factors are common in type 2 diabetes. Adequate treatment of the blood pressure and cholesterol levels are as important as managing the glucose control to reduce the complications.
“Type 2 diabetes is often not diagnosed in the early stages due to lack of symptoms. As a consequence, approximately 50 per cent of people with type 2 diabetes have some form of complications at diagnosis.”
How to monitor and test your blood sugar levels
At home, the blood glucose level can be checked by the person with diabetes using a finger prick test with a blood glucose meter. This method checks the glucose level in the capillary blood obtained from the finger prick.
“It is important that the finger is clean and not contaminated by any glucose-containing material when this test is done,” says Dr Song “as otherwise, it can lead to erroneous results.
“This self-monitoring of blood glucose can help to guide diabetes treatment, especially with insulin injections, that will achieve a satisfactory glucose control.”
Do hot baths lower blood sugar levels?
There is evidence that hot baths do lower blood glucose levels. It could be a good alternative to exercise for some people who want to reduce their blood sugar levels. But doctors will point out that exercise is an important part of a healthy lifestyle.
Can diabetes affect your thinking?
Diabetes is associated with cognitive impairment but not everyone with diabetes will experience this. Older people with diabetes have been found to lose cognitive ability faster than those without the disease.