High Blood Glucose: Causes, Treatment and Prevention

Blood glucose is the sugar in your blood, and it's your body's main source of energy. When blood glucose stays too high for too long, it can damage your heart, kidneys, eyes and nerves, often without causing any symptoms for years. This guide explains normal levels, what pushes them up, the blood tests that find diabetes and prediabetes, and how high sugar levels are treated and prevented.

Key takeaways

• A normal fasting level is 5.4 mmol/L or under; 7.0 or more on two tests usually means diabetes.
• Type 2 diabetes is the most common kind in Australia, and it can often be prevented or delayed.
• Many people with high sugar levels feel well, so a blood test is the only way to know.
• Healthy eating, regular activity and medicines, including insulin when it's needed, bring levels back into range.

What Is Blood Glucose?

Glucose is the main sugar in your blood, made from the carbohydrates you eat, and insulin from your pancreas moves it into your cells for energy. So what is a regular blood sugar level? For adults without diabetes, it's usually 4.0 to 5.4 mmol/L after fasting, and under 7.8 two hours after a meal.

A result in between means more testing or a higher risk. Diabetes is usually diagnosed only after a second abnormal test, unless you have clear symptoms, and laboratories may report slightly different ranges.

How Diabetes Is Diagnosed With Blood Tests

Diabetes is found with a blood test, not by symptoms alone. The usual first test is a fasting glucose, taken after eight hours with nothing but water, or an HbA1c, which shows your average sugar level over about three months and needs no fasting. If a result is in between, a glucose tolerance test checks how your body handles a sugary drink over two hours. A result in the diabetes range is usually repeated to confirm it, unless you already have clear symptoms. Pregnant women have a glucose tolerance test at 24 to 28 weeks to check for gestational diabetes, a kind that starts in pregnancy, and people with an in-between result are usually retested every year.

What Makes Blood Glucose Rise Too High

Glucose rises too high when your body doesn't make enough insulin, or when its cells stop responding to insulin properly, which is called insulin resistance. Extra weight around the waist, too little activity, family history, getting older, some medicines such as steroids, and illness or infection can all push your levels up.

Your glucose also changes through the day with what you eat, how active you are, stress and sleep. What is a regular blood sugar after a big meal? In a healthy adult it usually stays under 7.8 mmol/L and falls back within a few hours, which is why a single reading after eating can mislead and a blood test for glucose, read by your doctor, gives a clearer answer.

Types of Diabetes and Prediabetes

There are three main types of diabetes. Type 1 diabetes is an autoimmune condition in which the pancreas stops making insulin, so people need insulin from diagnosis; it often starts in childhood or young adulthood but can begin at any age. Type 2 diabetes, which makes up about nine in ten cases in Australia, develops slowly as the body becomes resistant to insulin. Gestational diabetes starts in pregnancy and usually goes after the birth, though it raises the chance of type 2 later in life. Prediabetes means your glucose levels are higher than normal but not yet in the diabetes range, and it's the best time to act.

How High Blood Glucose Is Treated

Treatment aims to keep your glucose in a healthy range and protect your heart, kidneys, eyes and feet. For prediabetes and early type 2 diabetes, that often starts with healthy eating, regular activity and weight loss if you need it. Many people also need tablets or injections, and some need insulin; these medicines are prescription only in Australia, and your doctor chooses them with you. People with type 1 diabetes always need insulin, and everyone with the condition has regular checks of HbA1c, blood pressure, cholesterol, kidneys and eyes.

Preventing Type 2 Diabetes

Type 2 diabetes can often be prevented or delayed, especially if you act at the prediabetes stage. Insulin resistance usually starts years before the diagnosis, and losing 5 to 10% of your body weight if you carry extra, doing at least 150 minutes of moderate activity a week, eating more vegetables, wholegrains and legumes, cutting sugary drinks and not smoking all help your body use insulin better. Type 1 diabetes can't be prevented, because it's an autoimmune condition.

Typical symptoms of type 2 diabetes include feeling thirsty, passing more urine, tiredness, blurred vision, itchy skin or thrush, and cuts or infections that heal slowly. Many people have no symptoms at all, which is why checking your risk matters. Australians over 40, and Aboriginal and Torres Strait Islander people from 18, are advised to check their risk every three years, with a blood test if it's high.

When to See a Doctor About Your Sugar Levels

See a doctor about a diabetes test if you're very thirsty, are passing more urine or are losing weight without trying, if you're over 40 with risk factors, or if you've had gestational diabetes or have polycystic ovary syndrome. If you take insulin or other diabetes medicines, see your doctor about frequent lows or highs. Call 000 or go to an emergency department for vomiting, stomach pain, fast breathing, drowsiness or confusion with high sugar levels, or a low that doesn't improve after you've had sugar. If a child is very thirsty, passing lots of urine and losing weight, see a GP in person that day; Medio's doctors see adults 18 and over.

Summary

This guide covered normal blood glucose, the tests that find diabetes, and how high levels are treated and prevented. If you're worried about your blood glucose, a Medio GP can talk it through by phone, request a blood test, and send an eScript or a referral if they think it's right.

Frequently asked questions

What is the healthy blood sugar level in Australia?

For most adults, a healthy fasting level is about 4.0 to 5.4 mmol/L, and under 7.8 two hours after eating. What do blood glucose test results mean? A fasting result of 7.0 or more, or an HbA1c of 6.5% or more, points to diabetes, and your doctor explains what your own result means.

What is the #1 worst food for your blood sugar?

No single food is the worst, but sugary drinks, such as soft drinks, cordial and juice, raise blood sugar fastest because the sugar is absorbed so quickly. Lollies, white bread and other refined starches come close. What affects blood sugar levels? Food, activity, stress, sleep, illness and some medicines all play a part.

Can a doctor help with blood glucose?

Yes. A GP can check your risk, request a diabetes test such as a fasting glucose or HbA1c, explain the result and, if your levels are high, help you manage them with lifestyle changes and medicines where needed. A Medio GP can do this by phone, and refer you to a diabetes educator or dietitian if they think it's right.

Can GLP-1 cause low blood sugar?

On their own, GLP-1 medicines rarely cause low blood sugar, because they boost insulin only when glucose is high. The risk rises when they're taken with insulin or some other diabetes tablets, so your doctor may lower those doses. These medicines are prescription only in Australia. How do people with type 1 diabetes manage their blood sugar levels? With insulin, regular glucose checks and matching their doses to what they eat.

What flushes sugar out of your bloodstream?

Nothing flushes sugar out quickly. Insulin moves sugar from your blood into your cells, and exercise helps your muscles use it, which is why a walk after a meal can lower your level. Drinking water helps if you're dehydrated but doesn't treat high sugar. Very high levels with vomiting or drowsiness need a call to 000.

Are eggs good for lowering blood sugar?

Eggs don't lower blood sugar, but they have almost no carbohydrate, so they barely raise it and can be part of a healthy diet. Who is at risk of developing type 2 diabetes? People over 40, and those with extra weight, a family history, high blood pressure or past gestational diabetes. Is type 2 common? Yes, it's the most common kind.