High Blood Sugar: Signs, Tests and What to Do
High blood sugar, or hyperglycaemia, means blood glucose is above the recommended range. It may cause increased thirst, frequent urination, tiredness or blurred vision, although some people may have few or no obvious symptoms. A single home glucose reading cannot diagnose diabetes; repeated high readings or concerning symptoms should be discussed with a healthcare professional. [5, 7–10]
What high blood sugar means
High blood sugar, or hyperglycaemia, happens when the body has too little insulin or cannot use insulin properly. Blood glucose may also rise with factors such as eating more than planned, reduced physical activity, illness or stress. [10]
A high reading should be considered together with symptoms and the pattern of readings over time. Home glucose monitoring can help track blood glucose, but diabetes diagnosis requires appropriate testing in a healthcare setting. [5, 8, 9]
Common signs and symptoms of high blood sugar
Symptoms may develop gradually, particularly in type 2 diabetes, and some people may have few or no noticeable symptoms. Common signs can include: [7, 10]
- Feeling unusually thirsty
- Urinating more often than usual
- Feeling tired
- Blurred vision
- Unexplained weight loss
These symptoms can have other causes, so symptoms alone cannot confirm high blood sugar or diabetes. A blood glucose test is needed to know your glucose level. [7, 8]
When high blood sugar needs urgent care
If you are unwell and concerned about unusually high glucose readings or worsening symptoms, contact your healthcare team for advice.
How high blood sugar is tested
A finger-prick glucose meter shows your glucose at that moment and is useful for monitoring. Laboratory tests such as fasting plasma glucose, an oral glucose tolerance test and HbA1c are used to assess and diagnose diabetes. HbA1c reflects average blood glucose over the previous 2–3 months. [5, 8, 9]
A home glucose reading alone cannot confirm a diagnosis of diabetes. Test results should be interpreted by a healthcare professional together with your symptoms and overall health. [5, 8]
Why one home meter reading is not a diagnosis
A home glucose meter shows your blood glucose level at a particular point in time and is useful for ongoing monitoring. Results should be interpreted together with factors such as food intake, physical activity and patterns over time. [9]
A single home reading cannot confirm diabetes. If high readings occur repeatedly or you have symptoms that concern you, speak with a healthcare professional about appropriate clinical testing. [5, 9]
Blood sugar targets for people with type 2 diabetes
Blood glucose and HbA1c targets may be different from the values used to diagnose diabetes. The Malaysian Clinical Practice Guidelines recommend that glucose targets are individualised according to each person's health and risk of low blood sugar. For many adults with type 2 diabetes, an HbA1c target of around 7.0% or lower may be used, although a different target may be more appropriate for some people. [5]
Why blood sugar control matters
Persistently high blood sugar can contribute to damage to blood vessels and nerves over time. Diabetes-related complications may affect the eyes, kidneys, nerves, heart and brain. Good diabetes care therefore involves more than glucose alone and may also include monitoring blood pressure, cholesterol, kidney health, eye health and foot health. [1, 3, 5, 7]
| Area | Possible complication | Why follow-up matters |
|---|---|---|
| Eyes | Diabetic retinopathy | Early changes may cause no noticeable symptoms, so regular eye checks are important. [2] |
| Kidneys | Diabetic kidney disease | Urine and blood tests can help detect kidney changes early. [5] |
| Nerves and feet | Peripheral neuropathy and foot problems | Regular foot checks can help identify reduced sensation, wounds or circulation problems. [4, 5] |
| Heart and brain | Heart attack and stroke | Glucose, blood pressure, cholesterol and smoking status are all important parts of cardiovascular risk management. [5, 7] |
How to monitor blood sugar safely at home
Self-monitoring of blood glucose refers to checking blood glucose at home and can help you understand patterns in your readings over time. It may also help show how factors such as food, physical activity and your diabetes care plan relate to your glucose levels. It is important for those who use insulin. The frequency and timing of checks should be based on individual needs, medicines, glucose patterns and treatment goals. [5, 6, 9]
- Follow the instructions provided with your glucose meter and test strips.
- Wash and dry your hands before testing.
- Record your readings and note factors such as meals, physical activity or stress that may help explain patterns.
- Discuss repeated high or low readings with your healthcare team. [9]
What to do if your reading is high
A single high reading should be considered together with your usual glucose range, symptoms and pattern over time. Keep a record of repeated high readings and note factors such as food, physical activity or stress that may help explain the pattern. Discuss repeated high readings or concerning symptoms with your healthcare team. [9]
Practical ways to support steadier blood sugar
- Take prescribed medicines as directed and speak with your healthcare team if you have concerns about them.
- Aim for regular, balanced meals and follow the nutrition advice provided by your healthcare team.
- Include regular physical activity that is suitable for your health and abilities.
- Follow your sick-day plan, including glucose or ketone checks, as instructed by your healthcare professional.
- Keep a record of your glucose readings and discuss repeated high or low patterns with your healthcare team.
- Attend recommended follow-up checks, including HbA1c, blood pressure, cholesterol, kidney, eye and foot assessments. [5, 7, 9]
Speak with a CARiNG pharmacist
A CARiNG pharmacist can help you use a glucose meter correctly, understand how to record readings, and recognise when it may be appropriate to seek further medical advice. You can also explore CARiNG chronic disease management or find a nearby store. Screening can help identify a possible risk, but it does not confirm a diagnosis of diabetes.
Useful resources
- Ministry of Health Malaysia – Clinical Practice Guidelines: Management of Type 2 Diabetes Mellitus, 6th Edition
- World Health Organization – Diabetes
- American Diabetes Association – Diabetes Diagnosis and Tests
- American Diabetes Association – Checking Your Blood Sugar
- American Diabetes Association – Hyperglycemia
Medical disclaimer: This article is for general health education and does not replace medical advice, diagnosis or treatment. Blood glucose targets and monitoring plans should be individualised. Speak with a qualified healthcare professional if you have concerns about your readings or overall diabetes care. Seek urgent medical attention for severe symptoms or if you are becoming rapidly unwell.
Frequently asked questions about high blood sugar
Can stress cause high blood sugar?
Yes. Physical or emotional stress can raise blood glucose, and illness or infection can have a similar effect. If high readings persist or happen repeatedly, discuss them with your healthcare team rather than assuming stress is the only cause. [10]
What should I do if my blood sugar is high but I feel well?
A single high reading should be considered in context. Record the result and look for patterns over time. If high readings occur repeatedly or stay above your usual target range, discuss them with your healthcare professional. [9]
How often should I check my blood sugar?
There is no single schedule for everyone. How often you check depends on factors such as your diabetes treatment, glucose patterns and individual goals. Follow the monitoring schedule recommended by your healthcare team. [5]
When does high blood sugar need urgent medical attention?
A glucose number alone may not determine whether the situation is an emergency. Seek urgent medical care if high blood sugar is accompanied by shortness of breath, fruity-smelling breath, nausea or vomiting, or a dry mouth, as these may be warning signs of diabetic ketoacidosis. [10]
Can I exercise if my blood sugar is high?
Physical activity can help with glucose management, but exercise may not be appropriate when ketones are present. Follow the monitoring and activity advice provided by your healthcare team, especially if you are unwell or have unusually high readings. [10]
View references 10 sources
- American Diabetes Association. Diabetes Overview: Complications. Original source reference, accessed June 2021. Current page: Source
- National Eye Institute. Diabetic Retinopathy. Original source reference, accessed June 2021. Current page: Source
- Cade WT. Diabetes-Related Microvascular and Macrovascular Diseases in the Physical Therapy Setting. Physical Therapy. 2008;88(11):1322-1335. Source
- Cleveland Clinic. Peripheral Neuropathy. Original source reference, accessed June 2021. Current page: Source
- Ministry of Health Malaysia. Clinical Practice Guidelines: Management of Type 2 Diabetes Mellitus. 6th edition. 2020. Source
- Diabetes.co.uk. Self Monitoring of Blood Glucose. Original source reference, accessed June 2021. Retained for source traceability; not used as the main authority for clinical thresholds. Source
- World Health Organization. Diabetes. Updated 14 November 2024. Accessed 5 November 2026. Source
- American Diabetes Association. Diabetes Diagnosis and Tests. Accessed 5 November 2026. Source
- American Diabetes Association. Checking Your Blood Sugar. Accessed 5 November 2026. Source
- American Diabetes Association. Hyperglycemia. Accessed 5 November 2026. Source
Latest Health Info
High Blood Sugar: Signs, Tests and What to Do
The short answer High blood sugar, or hyperglycaemia, means blood glucose is above the recommended range. It may cause increased ...
Low Blood Sugar: Signs, 15-15 Rule and When to Get Emergency Help
The short answer Low blood sugar, also called hypoglycaemia, generally refers to a blood glucose level below 3.9 mmol/L. Common ...
Which Blood Sugar Supplement Is Right for You?
Written by: Jeremy Se, Senior Dietitian, Cambert (M) Sdn Bhd Sponsored by: Kordel’s Short answer Start with the specific concern ...