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Low Blood Sugar – Hypoglycemia 101

Published: 3/15/21
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By Eliza Skoler and Matthew Garza

What are the symptoms of low blood sugar? What causes low blood sugar and how can you prevent it? What should you do if your blood sugar is low?

What is Hypoglycemia (Low Blood Sugar)?

For adults and children with diabetes, hypoglycemia (low blood sugar) is defined as a glucose value below 70 mg/dL. Hypoglycemia is a challenge to the body – our cells need to get glucose from the bloodstream to use for energy, and when blood sugar is low, there is not enough glucose for the cells. While hypoglycemia can be quite dangerous, most people with diabetes are able to recognize the signs and symptoms of hypoglycemia as their glucose levels are trending low before severe hypoglycemia occurs.

There are three levels of hypoglycemia: level 1, glucose values less than 70 mg/dL; level 2, glucose levels less than 54 mg/dL; and level 3, referred to as severe hypoglycemia, in which glucose levels are so low that mental or physical functioning is impaired and the person requires assistance.

What is dangerously low blood sugar?

Severe hypoglycemia occurs when your body can’t function properly because glucose is too low. In these extreme cases, low blood sugar can cause you to become confused or even to lose consciousness (when there is not enough glucose for the brain to adequately function). Severe hypoglycemia is characterized by a change in your mental state or the need for someone to help you treat the extreme low.

You should always treat lows right away, whether your blood sugar is below 70 mg/dL or trending toward that number. If your glucose levels drop below 54 mg/dL (level 2 hypoglycemia), you should act immediately to raise your blood sugar and prevent prolonged exposure to hypoglycemia.

What is glucose and why is it so important?

Glucose is a simple sugar, a component of the carbohydrates found in most foods. When broken down, glucose is the main form of energy for the body, particularly for our muscles and brain – it’s the fuel that the brain runs on. Though glucose is necessary for the body, the amount of glucose in the blood (your blood sugar) must be tightly regulated: too much or too little glucose in the blood can lead to hypoglycemia, hyperglycemia, and long-term health complications. As glucose circulates in the blood and comes into contact with muscle and fat cells, insulin is required to allow glucose to enter the cells to be used or stored for energy. Between meals, the liver produces glucose to fuel the body.

Low Blood Sugar Symptoms

Though not everyone experiences the same symptoms during hypoglycemia, it’s important to try to notice what occurs in your body when your blood sugar is low. These are some of the common symptoms of hypoglycemia:

  • Hunger

  • Sweating

  • Shaking

  • Fast heartbeat

  • Headache

  • Trouble concentrating

  • Fatigue

  • Irritability 

  • Confusion

During severe hypoglycemia you may experience different symptoms that indicate that your brain doesn’t have enough glucose to properly function:

  • Confusion

  • Combativeness 

  • Disorientation

  • Seizures

  • Loss of consciousness

How do you feel if your blood sugar is low?

If your blood sugar is low, you may feel “out of it” – confused, annoyed, and without focus. You should treat lows immediately, whether your glucose is below 70 mg/dL or trending toward that number, and whether or not you are feeling symptoms.

It’s important to take hypoglycemia seriously. Read on to learn what to do when your blood sugar is low.

What is hypoglycemia unawareness?

Some people experience hypoglycemia unawareness (which can also be called reduced hypoglycemia awareness) – this means the body doesn’t release or respond to the warning signals of hypoglycemia, putting them at risk of prolonged low glucose levels. Several factors can increase your chances of hypoglycemia unawareness, including having repeated episodes of hypoglycemia, going low while sleeping, exercising, consuming alcohol, having specific diabetes complications (like neuropathy), or taking certain medications. Because hypoglycemia unawareness more often occurs in those who were diagnosed with diabetes decades before, in addition to the risk factors mentioned, it commonly occurs in people over the age of 65.

Can a continuous glucose monitor help with low blood sugar?

A continuous glucose monitor (CGM) measures the body’s glucose levels in real-time by sensing the glucose present in tissue fluid (also called interstitial fluid). A CGM typically provides your glucose level every five minutes, which can be really helpful for tracking and finding patterns in how your glucose changes throughout the day. With CGM you can see how much time you spend in your target glucose range each day (Time in Range), notice trends, and develop strategies to improve your diabetes management. 

CGMs can sound alerts when glucose levels drop (or rise) below a certain threshold or are predicted to do so soon. This can be especially helpful for people who experience hypoglycemia unawareness, nighttime low blood sugar, or frequent hypoglycemic events. CGMs also allow you to share your glucose readings with your loved ones and care-partners in real time, so that they can let you know or help you out if your blood sugar starts to drop.

If you are interested in trying CGM, ask your healthcare team if the technology is available to you. You can also try ten-days of CGM for free.

What causes low blood sugar?

Hypoglycemia is usually a result of diabetes treatment, often because there is too much insulin in the body.

Here are some reasons why hypoglycemia might occur:

  • Too much insulin administered for your body’s needs at the time.

  • Sulfonylureas stimulate insulin release from the pancreas, even if your glucose levels are in range –­ this can lead to low blood sugar.

  • Too high levels of diabetes medications. If you are taking glucose-lowering drugs in combination with sulfonylureas or insulin, these medications can lower your blood sugar and increase your risk for hypoglycemia.

  • Not enough food, particularly carbohydrates.

  • Too much exercise at one time, particularly mild to moderate aerobic exercise. This is because exercise can increase your sensitivity to insulin, which allows your muscle cells to take up glucose from your bloodstream.

  • Illness, particularly if associated with vomiting, nausea, and diarrhea.

  • Other medical conditions, including some liver and kidney illnesses, eating disorders, and certain hormone deficiencies.

What do you do when blood sugar is low?

If you notice that your blood sugar is low, it is important to treat it right away to prevent it from dropping even further. Here are some strategies you can use to treat low blood sugar, but it’s best to discuss these with your healthcare team before trying them:

  • Have an emergency hypoglycemia kit that is easily accessible and with you at all times. Make sure people you are with know what to do in a hypoglycemic emergency. Your kit should include:

    • Glucose tablets or sugary snacks

    • Glucagon – read about emergency nasal glucagon (Baqsimi) and ready-to-use autoinjector pens (Gvoke)

    • Glucose monitor (continuous glucose monitor or fingerstick blood glucose meter)

    • Emergency contact information

If you are not carrying a full emergency kit, make sure to at least carry glucose tablets or sugary candies.

  • Use the 15-15 rule. Eat or drink 15 grams of carbohydrates (glucose tablets, 4 oz of juice, 1 tablespoon of sugar or honey, small hard candies, etc.) to raise your blood sugar. Check it after 15 minutes. If it’s still below 70 mg/dL, have another serving of 15 grams of carbs.

    • Repeat these steps until your blood sugar is at least 70 mg/dL. Once your blood sugar is back in range, you might consider eating a snack with little or no insulin to make sure it doesn’t drop again. If you eat a snack, make it a small, protein-rich snack, and be careful of rebound high glucose levels.

    • If you use a closed loop device, discuss with your healthcare team if you should take less than 15 grams to correct a low glucose value. 

  • In severe cases, when a person is vomiting, not able to cooperate or coordinate swallowing, or not fully conscious, glucagon should be used to treat hypoglycemia. Glucagon is a natural hormone that tells the body to release stored sugar into the bloodstream. Emergency glucagon is available by prescription and can be injected or administered into the nose.

What is the best thing to eat when your blood sugar is low?

To avoid overtreating lows with too much simple carbohydrate or food and then facing a rebound high blood sugar, it’s best to have go-to automatic corrections for hypoglycemia that are quantity limited and unappealing to overeat. Glucose tablets and gels, and candies like Smarties, are predictable, relieve low symptoms quickly, and are hard to overeat. Some people with diabetes count out jelly beans, mini-Swedish Fish, gummies, or hard candy and eat the exact amount that will help their blood sugar. Others take a specific amount of juice or another sugar-containing drink.

How do you know how much of your correction to consume? Similar to the 15-15 rule, the only way to discover exactly how much of your go-to correction your body needs is by checking your glucose levels, eating a source of sugar that has been measured out, and then checking again in roughly 15 minutes. This can help you adjust the amount of your source of sugar to raise your blood sugar to your target (say, 100 mg/dl), but not overshoot. This is a precision dose of carbs. To learn more, read Adam Brown’s “Defeating the Hypoglycemia Binge.”

Do not use a low as a reason to eat treats – this can cause your blood sugar to spike later. Plus, it connects a food reward (treat) with something you want to avoid (going low), which is an easy way to develop a bad habit.

How can you prevent low blood sugar?

The best way to prevent glucose levels that are too low is to practice careful diabetes management, checking your glucose often (either with a blood glucose meter or a continuous glucose monitor), and learning to recognize its early symptoms. Pay attention to the helpful arrows on your blood glucose meter or CGM – if the arrow is pointing down, you’ll want to monitor your blood sugar to make sure you don’t go low.

To learn more about preparing for low blood sugar events, read “Hypoglycemia Preparedness: How to Know Before You Go Low."

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