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Blog - Diabetes Information, Symptoms & Diagnoses

What are the Symptoms of High Blood Sugar Levels

Maintaining healthy glucose levels is an essential part of diabetes management. Hyperglycaemia (high blood sugar) occurs when your body has too little insulin or cannot sufficiently use available insulin, causing your blood sugar levels to rise. Without action, high blood sugar can be fatal.
While healthy blood sugar concentration varies from person to person, hyperglycaemia typically refers to a person with blood glucose levels greater than 7 mmol/L after waking up or not eating or more than 11 mmol/L at any other time1.
Continuous glucose monitoring (CGM), as Dexccom rtCGM systems can help those with type 1 and type 2 diabetes to prevent both hyperglyceamia (Hypers, high blood sugar symptoms) as well as hypoglycaemia (hypos, low blood sugar symptoms).2,3,4,5
The first signs of high blood sugar are also the first signs of diabetes and include:
  • thirst1
  • fatigue1
  • feeling weak1
  • tiredness and lethargy1,6
  • problems with vision1
  • blurred vision1
  • weight loss1,6
  • frequent urination1
Mild symptoms that are not identified and treated can accumulate over time. If high blood sugar levels are left untreated, hyper diabetes symptoms can become severe or even life threatening.
Symptoms and complications (long-term complications) of unmanaged hyperglycaemia can include:1,6,7,8
  • skin infections, such as staphylococcus7,8
  • slow-healing skin injuries7
  • diabetic ketoacidosis, with symptoms of nausea, vomiting or abdominal pain1,2,6,8
  • hyperosmolar hyperglycaemia state (HHS) with symptoms including dehydration and loss of consciousness8
  • long-term damage to the eyes, heart, kidneys, nervous system and blood vessels1,6,8
What causes high blood sugar levels?
Slight fluctuations in blood sugar levels are normal, depending on your everyday activities and eating habits.
Raised blood sugar levels routinely occur if you do not have enough insulin in your body or if available insulin is insufficiently used by your body. However, several factors can result in high blood sugar levels, including:
  • your family history (particularly for those with diabetes)
  • your lifestyle, such as poor diet and inactivity
  • stress (increased levels of the hormones glucagon and cortisol)
  • taking certain medications, such as some steroids or immunosuppressants
  • pregnancy and gestational diabetes
How to lower your blood sugar
If you have diabetes, take fast-acting insulin as prescribed by your GP. Once taken, test your blood sugar levels once more within 15-30 minutes to ensure your blood sugar is reducing.
If you have diabetes, please consult your GP or diabetes consultant for treatment advice. Common strategies to reduce you blood sugar level include:
  • insulin1,6
  • exercise1,6
  • certain medications1,6
  • dietary advice1,6
How to prevent high blood sugar
The phrase, ‘prevention is better than the cure’ has never been truer when it comes to diabetes management and reducing the risk of developing diabetic hyperglycaemia induced long-term complications.
If you have high blood sugar readings, it is recommended to maintain an active lifestyle with regular exercise alongside a healthy diet with a low glycemic index. This means:
  • avoiding starchy foods1,9
  • reducing the number of sugary snacks in your diet1,9,12
  • increasing your fibre intake to slow the absorption of sugars11
  • eating healthy fats, such as nuts, seeds and fatty fish like salmon and cod9
  • remaining hydrated so your kidneys actively remove excess sugars9,12
Continuous Glucose Monitoring (CGM) systems can help you to identify any significant changes and allow you to take preventative measures to keep your blood sugar levels within a healthy range.2,3,4,5
Other described preventative steps include1:
  • reducing your stress levels
  • improving your quality of sleep
  • taking the correct dosage of any medication prescribed to help you regulate your blood sugar levels
  • following your diabetes plan set out with your healthcare provider
Monitor glucose levels with a Dexcom CGM system
Highly versatile, and with the ability to alert you of any significant fluctuations in your glucose levels with zero finger pricks*, Dexcom Continuous Glucose Monitoring (CGM) Systems can help you to manage your diabetes and may increase your time in a healthy glucose range4,5. Clinically proven to lower HbA1c2,3,4,5 users can remotely check glucose readings, anytime, anywhere with a compatible smart device –effective and convenient diabetes management for ultimate peace of mind13.

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References and Footnotes
*Finger pricks are required for diabetes treatment decisions if symptoms or expectations do not match readings
† Display devices sold separately. For a list of compatible smart devices, please visit 
**Historical results based on Dexcom G4 PLATINUM/ Dexcom G5 Mobile CGM System
1 NHS. High blood sugar (hyperglycaemia). Updated 26 May 2022. Accessed 26 January 2023.
2 Heinemann L, et al. Real-time continuous glucose monitoring in adults with type 1 diabetes and impaired hypoglycaemia awareness or severe hypoglycaemia treated with multiple daily insulin injections (HypoDE): a multicentre, randomised controlled trial. Lancet. 2018;391(10128):1367-1377.
3 Aleppo G, et al. The Effect of Discontinuing Continuous Glucose Monitoring in Adults With Type 2 Diabetes Treated With Basal Insulin. Diabetes Care. 2021;44(12):2729-2737.
4 Beck RW, et al. Effect of continuous glucose monitoring on glycemic control in adults with type 1 diabetes using insulin injections: The DIAMOND randomized clinical trial. JAMA. 2017;317(4):371-378.
5 Beck RW, et al. Continuous glucose monitoring versus usual care in patients with type 2 diabetes receiving multiple daily insulin injections: A randomized trial. Ann Intern Med. 2017;167(6):365-374.
6 Mouri M, et al. Hyperglycemia. Updated 28 April 2022. Accessed 26 January 2023.StatPearls [Internet].
7 Nagendra L, et al. Bacterial Infections in Diabetes. Updated 5 April 2022. Accessed 26 January 2023. Endotext [Internet].
8 Mayo Clinic. Hyperglycemia in diabetes. Published 20 August 2022. Accessed 26 January 2023.
Mayo Clinic.
9 NIH. Diabetes Diet, Eating, & Physical Activity. Updated December 2016. Accessed 26 January 2023.
10 Vedantam D, et al. Stress-Induced Hyperglycemia: Consequences and Management. Cureus. 2022 Jul 10;14(7):e26714.
11 Reynolds A.N, et al. Dietary fibre and whole grains in diabetes management: Systematic review and meta-analyses. PLoS Med. 2020 Mar 6;17(3):e1003053.
12 Kidneys and Diabetes. Updated 10 June 2022. Accessed 26 January 2023.
13 Lind M, Polonsky W, Hirsch IB, Heise T, Bolinder J, Dahlqvist S, et al., Continuous Glucose Monitoring vs Conventional Therapy for Glycemic Control in Adults With Type 1 Diabetes Treated With Multiple Daily Insulin Injections: The GOLD Randomized Clinical Trial. JAMA. 2017 Jan 24;317(4):379-387.

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