Insulin Therapy And Hypoglycemia

  • Yuna Chow BSc (Hons), Medicine, University of St Andrews

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The hormone insulin plays a crucial role in managing the body's blood sugar levels and is involved in various metabolic functions. 

When the body cannot produce sufficient insulin, supplemental insulin is given. This helps the patient maintain normal sugar levels, preventing damage to various organs.1

Various conditions involve insufficient insulin levels in the body, and this is commonly referred to as diabetes. Examples are:

  • Type 1 diabetes mellitus
  • Type 2 diabetes mellitus
  • Prediabetes
  • Gestational diabetes
  • Metabolic syndrome

Hypoglycemia means low blood sugar. ‘Hypo’ means less of something, ‘glyc’ comes from glucose, and ‘emia’ refers to something that is present in the blood. Blood sugar levels less than 70 mg/dL is considered to be a hypoglycemic state.2 3 4 

With the use of insulin and some anti-diabetic drugs, there is a risk of hypoglycemia. This article will discuss how insulin use can cause hypoglycemia, signs and symptoms of hypoglycemia, treatment, and prevention of hypoglycemia.  

Causes of hypoglycemia in Insulin-treated patients

In most cases, the insulin dose is well regulated by the healthcare provider and hence the chances of hypoglycemia are minimal. 2 3 4 

The causes include:

  • Overdose of insulin : An increased dose of insulin taken accidentally can cause hypoglycemia.  
  • Reduced dietary carbohydrate intake: Eating or drinking less carbohydrates can decrease the blood sugar alongside insulin maintaining it.
  • Fasting: With insulin, fasting can further reduce the blood sugar to life-threatening levels. 
  • Increasing physical activity without increasing food intake can lead to hypoglycemia.
  • Alcohol intake without enough food can also cause reduced blood sugar levels.
  • Other illnesses causing people to eat less food
  • Skipping meals.2 3 4 

Signs and symptoms of hypoglycemia

The presentation of hypoglycemia is very vague and confusing. When a patient has insulin therapy, the healthcare provider ensures the patient is aware of the potential risk of hypoglycemia. Most patients are advised to regularly check their blood sugar levels using a glucometer at home to prevent hypoglycemia and inform their healthcare provider if there is something unusual.2 3 4 5 Commonly, hypoglycemia has the following symptoms, depending on the severity:

  • Dizziness
  • Lightheadedness
  • Headache
  • Hunger
  • Restlessness
  • Sweating
  • Nausea
  • Vomiting
  • Tiredness
  • Confusion  
  • Increased heart rate
  • Palpitations
  • Anxiety
  • Cardiac arrhythmias (Irregular heart beats)
  • Fainting
  • Seizures
  • Coma
  • Death  2 3 4 5

Managing hypoglycemia

Mild to moderate hypoglycemia should be treated as soon as possible as it can become severe with time.3 4 5 6 Patients are advised to use the 15-15 rule by the American Diabetes Association, which includes:

  • Eat or drink 15 grams of fast-acting carbs – this includes glucose syrup, glucose tablets, oral glucose gel, table sugar, sugary fruit juice, and soda.
  • Check your blood sugar levels after 15 minutes.
  • Have another 15 grams of fast-acting carbs if the levels are still below 70 mg/dL.
  • Repeat till blood sugar is at least 70 mg/dL. 
  • Go to the hospital or call for help if symptoms worsen.

Patients are advised to keep fast-acting carbohydrates and a glucometer with them if they’re on insulin therapy to avoid hypoglycemia.4 5 6 

When there is severe hypoglycemia (<54 mg/dL), glucose alone cannot help treat it. Due to the urgency of this condition, doctors advise the patients to keep an emergency glucagon pen. Glucagon is a hormone that is opposite to insulin. It raises blood sugar levels. An emergency glucagon pen can be used by family members as well as the patient can be unconscious. It is a great safety measure that can save lives.7 8

There are also glucagon nasal sprays – they don’t require the patient to inhale as glucagon is pushed into the airway.4 5 6

Common fast-acting carbohydrates

Here are some examples of fast-acting carbohydrates:

  • Half a regular sized banana.
  • 1 tablespoon of sugar, honey, or maple syrup. 
  • 1 tube of instant glucose tube.
  • Half a cup of sugary soda.
  • Half a cup of sweetened fruit juice.

Prevention measures

Awareness about the risk of hypoglycemia with patients on insulin is paramount. 9 Patients should know about the following:

  • Signs and symptoms of hypoglycemia so that they can treat the condition before it gets worse.
  • Maintaining a steady, well-calculated diet, also known as meal planning. This is done with a dietician or a healthcare provider or both to avoid hypoglycemia. 
  • Not skipping meals or fasting without consulting the doctor, even for surgery or blood tests.
  • If signs of illness appear, informing the doctor right away can help prevent this condition. 7 8
  • Keeping their blood glucose in check using a glucometer. 
  • Learning how to use an emergency glucagon pen (also for friends and family).
  • Checking glucose levels before driving or other high risk activities.
  • Keeping fast-acting carbohydrates readily available. 
  • Do inform the doctor if starting other medications that can alter the blood glucose levels.
  • Get a continuous glucose monitoring device if they have frequent incidents of hypoglycemia.9
  • People with liver and kidney disease should be more cautious.
  • Carry a medical ID in case found unconscious with instructions for glucagon pen administration.4 5 6 


Insulin is an important hormone that plays a major role in regulating blood sugar levels and various metabolic functions. Conditions where the body cannot produce sufficient insulin are commonly referred to as diabetes, including type 1 and type 2 diabetes mellitus, prediabetes, gestational diabetes, and metabolic syndrome. 

Hypoglycemia is defined as having low blood sugar levels. It becomes a concern particularly in insulin-treated patients. The causes of hypoglycemia range from excessive insulin doses to reduced carbohydrate intake, fasting, increased physical activity without an adequate diet, alcohol consumption without sufficient food, other illnesses affecting appetite, and skipping meals. 

Recognizing the signs and symptoms of hypoglycemia is key and includes dizziness, sweating, confusion, and even life-threatening conditions such as seizures or coma. 

Managing mild to moderate hypoglycemia involves the 15-15 rule, which recommends taking 15 grams of fast-acting carbohydrates, checking blood sugar levels after 15 minutes, and repeating until levels are stabilised. 

Severe hypoglycemia may require an emergency glucagon pen, a hormone that raises blood sugar levels, or a nasal glucagon spray. 

Preventive measures include maintaining awareness of one’s risk of hypoglycemia, following a specific diet, avoiding skipping meals, informing healthcare providers of signs of illness, regular blood glucose checks using a glucometer, learning to use an emergency glucagon pen, and carrying fast-acting carbohydrates. 

Additional precautions include checking glucose levels before high-risk activities like driving, obtaining continuous glucose monitoring devices in cases where there are frequent incidents of hypoglycemia, and being more cautious if one has liver and kidney diseases. 

Overall, education and preventative measures are essential to minimise the risk of hypoglycemia in individuals on insulin therapy.


Q. How common is hypoglycemia?

  1. According to a global study involving individuals using insulin for diabetes, approximately 4 out of 5 individuals with type 1 diabetes and nearly half of those with type 2 diabetes had at least one episode of low blood sugar over a 4-week period. However, severely low blood glucose, characterised by a level so low that self-treatment becomes hard, is less frequent in these groups. In the United States, among adults with diabetes who use insulin or medications that help release insulin, around 2 out of 100 individuals can have severely low blood glucose annually.

Q. How to know if you have low blood glucose during sleep?

  1. Common symptoms include:
    • Nightmares
    • Sweating a lot
    • Feeling tired after waking up
    • Low mood


  1. Cleveland Clinic [Internet]. [cited 2024 Jan 19]. Insulin: what is it, how do you take it, side effects. Available from:
  2. McCall AL. Insulin therapy and hypoglycemia. Endocrinol Metab Clin North Am. 2012 Mar;41(1):57–87.
  3. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. [cited 2024 Jan 19]. Low blood glucose (Hypoglycemia) - niddk. Available from:
  4. Hypoglycemia clinical presentation: history, physical examination [Internet]. [cited 2024 Jan 19]. Available from:
  5. Hypoglycemia in insulin-treated patients [Internet]. [cited 2024 Jan 19]. Available from:
  6. Lamounier RN, Geloneze B, Leite SO, Montenegro R, Zajdenverg L, Fernandes M, et al. Hypoglycemia incidence and awareness among insulin-treated patients with diabetes: the HAT study in Brazil. Diabetology & Metabolic Syndrome [Internet]. 2018 Nov 21 [cited 2024 Jan 19];10(1):83. Available from:
  7. Cleveland Clinic [Internet]. [cited 2024 Jan 19]. Hypoglycemia. Available from:
  8. [Internet]. 2017 [cited 2024 Jan 19]. Low blood sugar (Hypoglycaemia). Available from:
  9. Uptodate [Internet]. [cited 2024 Jan 19]. Available from:

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Meenakshi Khatri

Bachelor of Medicine, Bachelor of Surgery (M.B.B.S)

Dr. Meenakshi blends her clinical practice with scholarly pursuits. She works as a clinical assistant (junior doctor) in a cardiology practice in India. She actively contributes to medical knowledge and recently authored a chapter on antioxidants in a book publication. Her goal is to focus on both practical patient care and advancing medical understanding. presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
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