What Causes Low Blood Sugar (Hypoglycemia)?
Medically reviewed by Jonathan B. Jassey, DO
Hypoglycemia, or low blood sugar, causes symptoms like confusion, irritability, and shakiness. Diabetes is one of the most common causes of low blood sugar. It's rare for people without diabetes to have low blood sugar, but it's possible. Other causes include hormone deficiencies and liver disease.
Low blood sugar can decrease quality of life and be harmful. Symptoms can lead to a fall or other injury. Low blood sugar can become a medical emergency in severe cases. Here are the causes of low blood sugar, as well as how to raise your blood sugar.
Related: 10 Unusual Symptoms of Diabetes
Diabetes
People with diabetes develop low blood sugar when there is not enough glucose (sugar) in the bloodstream to supply the body with energy. This can happen for a variety of reasons, such as:
Drinking alcohol
Exercising (depending on the intensity and duration)
Missing or delaying meals
Not eating enough carbs
Taking too much diabetes medication (e.g., insulin)
People with diabetes who use insulin or oral medications that increase insulin secretion have the highest risk for low blood sugar. Insulin is a hormone that helps your cells take in glucose. A study published in 2016 found that 83% of people with type 1 diabetes and 46.5% of those with type 2 diabetes who use insulin reported low blood sugar at least once over four weeks.
Genetic Disorders
Low blood sugar is common in people with congenital hyperinsulinism, which affects 1 in 50,000 newborns. This genetic disorder causes the body to produce too much insulin. Low blood sugar often occurs after skipping meals or exercising. Some develop low blood sugar after eating.
Hormone Deficiencies
Certain hormone deficiencies may lead to low blood sugar. These include a lack of cortisol, growth hormone, or thyroid hormone.
Cortisol is the stress hormone and triggers the release of glucose. Growth hormone is responsible for cartilage and bone growth during adolescence. The hormone also helps control your blood sugar levels. Thyroid hormone aids in several bodily functions, including growth and metabolism.
Liver Disease
Cirrhosis is scarring of the liver. Scar tissue affects the liver's ability to digest food and store energy, which can affect your blood sugar. Research has found that cirrhosis is commonly associated with insulin resistance, which can raise blood sugar. The pancreas releases more insulin to help glucose enter your cells. Medications that help control your blood sugar may result in low blood sugar.
Reactive Hypoglycemia
Reactive hypoglycemia causes low blood sugar two to five hours after eating. It's unclear what causes reactive hypoglycemia. People who drink alcohol, have tumors, or recently had surgery (e.g., weight-loss surgery) may be more likely to develop the health condition.
Is Low Blood Sugar Hereditary?
Certain health conditions that result in low blood sugar may be hereditary. Congenital hyperinsulinism, for example, runs in families. Research has shown that mutations in the ABCC8 gene, which helps release insulin, are a common cause of this genetic disorder. Mutations in the KCNJ11 gene less commonly result in congenital hyperinsulinism.
There's also a genetic component of diabetes. The inheritance pattern of type 1 diabetes is unclear, but mutations in the HLA-DQA1, HLA-DQB1, and HLA-DRB1 genes increase risk. These genes aid in immune function. The risk of type 2 diabetes increases if you have several family members with the disease. There are about 150 possible genetic mutations that may cause type 2 diabetes.
Who Gets Low Blood Sugar?
Some people are more likely to develop hypoglycemia than others, including:
Age: Research has found that low blood sugar is common in older adults aged 75 and older. Hypoglycemia symptoms increase the risk of falls and severe injuries.
Ethnicity: A study published in 2018 found that hypoglycemia rates are highest among Black adults. The researchers noted that disparities in the quality of care between Black and White adults are a possible risk factor. People of African descent may have a type of hemoglobin that affects A1C tests, which measure blood sugar levels.
Sex: Research has shown that women with type 2 diabetes are more likely to develop low blood sugar overnight than men. Other research has found that men with type 1 diabetes are likelier to have low blood sugar after strength training.
Risk Factors
Anyone can develop low blood sugar. It's normal for blood sugar to go up and down throughout the day. Some people, however, are likelier to develop hypoglycemia than others.
Cognitive Impairment
Research has shown that decreased cognitive function is common among older adults with diabetes. This includes reduced attention to detail, memory capacity, and planning skills. Cognitive impairment may lead older adults to neglect self-care, including diet, exercise, and blood sugar monitoring. Low blood sugar is more likely to occur as a result.
Heart and Kidney Disease
Severe cases of heart and kidney disease may lead to low blood sugar. Kidney disease, for example, affects your body's ability to filter your blood and remove waste. Medication may build up in your blood and lower your blood sugar levels.
Insulin
Low blood sugar is a side effect of insulin therapy, which is one of the most common ways to treat diabetes. This treatment, commonly available as a pen, pump, or syringe, helps replace the insulin that your body does not make. You must consistently check your blood sugar levels and adjust the amount of insulin you receive. Low blood sugar often occurs if you receive too much insulin.
Type 1 Diabetes
Low blood sugar is more common in people with type 1 diabetes than type 2. This is because people with type 1 diabetes must receive insulin therapy daily. People with type 2 diabetes, in contrast, only need insulin if other treatments cannot manage their blood sugar levels.
Related: How Can You Die From Untreated Diabetes?
How To Raise Low Blood Sugar
You can test your blood sugar levels if you have diabetes and develop low blood sugar symptoms. It's important to treat low blood sugar right away if you have low levels. You can consume rapid-acting carbs using the 15/15 rule.
Start with 15 grams (g) of carbs that contain sugar, such as:
1 tablespoon (tbsp) of honey, sugar, or jelly
4 ounces (oz) of any fruit juice or regular (non-diet) soda
Five to six pieces of hard candy
Three to four glucose tablets
Not everyone may need 15 g of carbs to stabilize their levels. Children, for example, may need fewer carbs than adults. Talk to a healthcare provider to figure out how much you need to consume to raise your blood sugar.
Avoid options that are high in fat, such as chocolate or candies with nuts. Your body may not metabolize high-fat food as quickly, and it can take longer to bring blood sugar up to safe levels.
Test your blood sugar levels after 15 minutes. Repeat the treatment if your blood sugar is still low. Eat a meal or snack that contains a complex carb, protein, and fat after your blood sugar starts to rise. Eat a sandwich on whole-grain bread with nut butter, cheese, or a protein source like chicken. You may opt for yogurt, nuts, and fruit or a meal-replacement bar if you are on the go.
A healthcare provider may prescribe glucagon if you have diabetes and an increased risk of low blood sugar. Glucagon is a hormone that raises severely low blood sugar when you are unable to follow the 15/15 rule. This is a life-saving prescription. Caretakers of children and adults with diabetes, school personnel, and camp counselors need to know how to use glucagon in case of an emergency.
What Blood Sugar Level Is Dangerous
It's normal for blood sugar levels to go up and down throughout the day. The typical blood sugar target for someone with diabetes is less than 180 milligrams per deciliter (mg/dL) within two hours of eating a meal. Low blood sugar is less than 70 mg/dL but at least 54 mg/dL. It's dangerous if your blood sugar is less than 54 mg/dL.
Low blood sugar symptoms may be subtle or hard to detect. Not knowing you have low blood sugar can delay treatment and cause your blood sugar to drop to dangerous levels. Late-stage symptoms are more serious and obvious, such as loss of coordination, personality changes, and weakness.
Make sure you have access to a blood glucose monitor if you have diabetes. People with diabetes also use various forms of continuous glucose monitors (CGMs) to track their blood sugar. You can use the blood glucose monitor to confirm low blood sugar. Ask a healthcare provider about how to handle low blood sugar when using a CGM.
A Quick Review
Low blood sugar is common among people with diabetes. Although rare, people without diabetes can develop low blood sugar. Other causes include hormone deficiencies and liver disease.
Understanding the causes of low blood sugar can reduce your risk and prevent it. Equip yourself and your loved ones with fast-acting carbs, glucagon, and glucose monitors to treat and prevent low blood sugar properly.
Frequently Asked Questions
1. What is dangerously low blood sugar?
Blood sugar is dangerously low when it reaches below 54 mg/dL. It's possible that having blood sugar this low can cause you to faint.
2. What should you eat when your blood sugar is low?
Follow the 15/15 rule to help raise low blood sugar. Consume 15 g of carbs and check your blood sugar after 15 minutes. Have another serving and test again if you have not reached your target blood sugar range after that time.
3. Does insulin lower your blood sugar?
Your body produces insulin to regulate blood sugar, keeping it from getting too high or low. Insulin is a common treatment for people with insulin resistance, such as those with diabetes.
4. Does exercise lower blood sugar?
Exercise can lower blood sugar both short- and long-term. Physical activity can lower blood sugar levels for up to one day after your workout. Exercise can help improve your A1C in the long term.
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