Person holding a receiver with cgm data displayed

Blog - Diabetes Information, Symptoms & Diagnoses

What Are the Symptoms of Low Blood Sugar Levels?

A "normal" blood sugar range will vary from person to person, but low blood sugar typically happens when levels fall below 4 mmol/L1. Low blood sugar is also known as hypoglycaemia or “hypo” – is not to be confused with hyperglycaemia or “hypers”, which refers to high blood sugar.
The body requires glucose for energy and if left untreated, low blood sugar levels can lead to significant long-term damage.
There are a range of initial diabetic hypoglycaemia (hypo) symptoms, which can include the following2:
  • sweating
  • palpitations
  • increased heart rate
  • tiredness
  • dizziness
  • trembling
  • hunger
  • tingling lips
If your low blood sugar is left untreated, symptoms can become advanced, including2:
  • blurred vision
  • impaired cognitive function
  • seizures
  • loss of consciousness
Severe hypoglycaemia can cause haemophilia and aphasia – symptoms that can be mistaken for a stroke. In extreme cases, untreated hypoglycaemia can be fatal3.
Hypoglycaemia is most common in those with type 1 diabetes but can occur in those with type 2 diabetes taking insulin or certain medications1.
If you have diabetes and take regular insulin, you may find initial symptoms are less noticeable. If you have type 1 diabetes and take regular insulin or have a history of low blood glucose levels, initial symptoms may be less noticeable – you may even miss the signs completely4. This is known as hypo unawareness, and it can lead to severe hypoglycaemia4. Symptoms can also occur at higher glucose values than in those without diabetes2. It is therefore important to regularly monitor your blood sugar levels and take action when they drop, even if you do not notice any symptoms.

What causes low blood sugar levels?

There are many circumstances which can lead to low blood sugar levels. The most common reason for low blood sugar is as a side effect of certain medications used to treat diabetes2. However, other common causes include3:
  • taking too much insulin
  • changes to your everyday schedule that could impact normal glycaemic control, such as skipping meals or travelling across various time zones
  • adopting a diet without sufficient carbohydrates
  • increased alcohol intake, which can affect the release of glucose into the bloodstream
  • intensive exercise, such as marathon running.

Types of low blood sugar

Although it is not as common, it is possible to experience low blood sugar without diabetes. Common causes of low blood sugar for those without diabetes include2:
  • Reactive hypoglycaemia (postprandial hypoglycaemia) – an overproduction of insulin, ordinarily within two to five hours after a meal
  • Malnutrition or eating disorders, such as anorexia nervosa
  • Weight loss surgery
  • Medical conditions, such as liver cirrhosis, kidney disease or advanced heart disease
  • Hormonal disorders that impact glucose regulation
  • Pregnancy complications, such as sickness or a history of low blood sugar which can lead to hypoglycaemia

How to treat hypoglycaemia

Gaining a greater awareness of potential hypoglycaemia (hypo) symptoms is essential to treat hypoglycaemia, alongside routinely self-monitoring blood glucose levels5.
For mild low blood sugar symptoms, or a reading of less than 4 mmol/L, consume 15g of fast-acting carbohydrates, such as a sugary drink or glucose tablets. After 15 minutes, check your glucose levels again and repeat these steps until you have blood glucose levels of 4 mmol/L or above, or within the target range agreed with your diabetes healthcare professional6.
Slow-release carbohydrates are required once your blood sugar level is no longer low. If possible, eat a main meal. Alternatively, eat some bread, toast or biscuits2.
If you have any advanced symptoms of low blood sugar or your levels are not improving after counteractions have been taken, you should seek immediate medical help.

Get low glucose alerts with a Dexcom CGM

Providing ease of use, Dexcom Continuous Glucose Monitoring (CGM) Systems can identify low glucose levels with zero finger pricks* or scanning and has been clinically proven to lower HbA1c and reduce hypoglycaemic incidents**,7.
Dexcom CGM systems offer a variety of alarms and alerts. The Dexcom G6 and Dexcom G7, for example, both include a predictive Urgent Low Soon Alert, which warns a user 20 minutes before levels will drop to 3.1 mmol/L. This can combat hypo unawareness and avoid a potentially severe hypoglycaemic event.
Allowing users to remotely check their glucose readings, anytime, anywhere with a compatible smart device, Dexcom CGM systems can also alert users whenever glucose levels fall outside of customised high or low glucose alerts, enabling users to take action.

Find the Dexcom CGM system for You

  • Compare Dexcom CGM systems
References and Footnotes
1 Diabetes and Hypoglycaemia. Published 8 September 2022. Accessed 29 November 2022.
2 NHS. Low blood sugar (hypoglycaemia). Updated 4 September 2020. Accessed 29 November 2022. NHS.
3 Mathew P, et al. Hypoglycemia (Nursing). StatPearls Publishing, Treasure Island (FL). Published 25 March 2021. Accessed 29 November 2022. Europe PMC.
3 Kalra, S, et al. Hypoglycemia: The neglected complication. Indian J Endocrinol Metab. 2013; 17(5): 819–834. NCBI.
4 Hypo Unawareness. Accessed 29 November 2022.
5 Lowe R, et al. Diabetes: how to manage patients experiencing hypoglycaemia. Published 14 June 2021. Accessed 16 February 2023. Drugs Context.
6 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. Published 16 February 2018. Accessed 16 February 2023. NIH.
*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 systems.

LBL-1002052 Rev001

© 2024 Dexcom, Inc. All rights reserved.

GB flag


Change region