Oftentimes when people have high blood sugar they blame whatever they last ate, but there are many reasons that could lead to high blood sugar. Yes, diet is one of the most important factors in controlling your blood sugars, but it is not the only one. Let’s take a look at all of the causes of high (and low) blood sugar.

Before we dig into the causes of blood sugar ups and down it is helpful to understand some blood sugar basics. The body uses glucose (sugar) in the body for energy. This sugar comes from the food we eat, particularly from carbohydrates such as grains, fruits, dairy, and beans. This sugar is used by all parts of the body including your brain, heart, and muscles.

When we digest the carbohydrates, our body breaks down these carbohydrates into glucose which is absorbed in the stomach and small intestine and then released into the bloodstream. Insulin, a hormone produced by the pancreas, transfers the glucose from the bloodstream into the cells for the body to use as energy. You may have heard of insulin been described as the “key” which unlocks the cell to let the glucose inside. When someone has an insufficient amount of insulin from diabetes or excess body weight, this glucose can build up in the bloodstream causing high blood sugar.

When the body has adequate insulin, blood sugar levels are kept between 70 and 120 milligrams per deciliter in a fasting state. After eating a meal, blood sugar levels can rise as high as 180 and within two hours after eating this level should drop to under 140. Keeping blood sugars balanced throughout the day helps us maintain our energy levels, keep our mood steady, and feel our best.

There are two different types of diabetes, type 1 and type 2. In type 1 diabetes, a person’s body does not make insulin and requires insulin injections to move glucose into cells. Type 2 diabetes occurs when the body has reduced the amount of insulin that it is made or is unable to use its own insulin very well (known as insulin resistance). About 90% of people with diabetes have type 2.

When glucose cannot enter the cells, it leads to hyperglycemia (high blood sugar), as this sugar builds up in the bloodstream causing blood sugar to rise. When blood sugars stay high, it can lead to a variety of health problems and also have a cascade of events in the body as it tries to lower the amount of sugar in the blood. If blood sugar levels remain too high for too long it can cause serious health problems if it is not treated. A single high blood sugar reading is not a cause for alarm, but if your blood sugars are consistently running high it’s important to talk with your healthcare team and take a good look at your lifestyle to see if there may be any changes that may help get your blood sugar levels back in control.

About 1 in 5 people with diabetes do not even know that they have it, around 7.3 million adults. Being familiar with these symptoms whether you have a diabetes diagnosis or not is important. It may help you spot the early signs of diabetes or help someone you know that has diabetes. Symptoms usually develop slowly but the longer blood sugars remain high the more serious these symptoms become.

Signs of High Blood Sugar

The following are signs that your blood sugar levels may be running too high:

• Frequent urination: The kidneys go into overdrive to try to flush out the extra glucose in the urine. Peeing more often and in larger amounts is a common sign that someone’s blood sugar is running high. Over time this can lead to dehydration and dry mouth. The hard work the kidneys put in to get rid of this extra sugar also wears them down and increases your risk for kidney disease.
• Increased thirst: Because someone may be losing a lot of fluid from urinating, they may feel extra thirsty. If you notice that you are struggling to quench your thirst or drinking a lot more than usual, it’s probably a good idea to get your blood sugar checked.
• Weight loss: If the body does not have enough glucose in the cells for energy because the glucose is stuck in the bloodstream, the body will break down muscle and stored fat in an attempt to fuel hungry cells. Fluid losses from increased urination can also cause a drop in weight and a loss of calories.
• Low energy, fatigue, and mood swings: Since body cells are not receiving glucose to use as energy, the body is left feeling drained and exhausted. The brain’s preferred energy source is glucose so when blood sugar levels are high (or low) the brain is not able to utilize the glucose causing brain fog and mood swings.
• Headache or blurred vision: Elevated blood sugar levels can lead to headaches or difficulty seeing.
• Feeling hungry all the time: Without glucose reaching cells the body feels extra hungry looking for glucose for fuel for the cells. Some people notice they still feel hungry after they finished an entire meal.
• Infections or wounds that don’t heal: Too much sugar in the blood can slow blood flow and make it harder for your body to heal. This reduction in blood flow lowers the amount of oxygen and nutrients being provided to the body to heal up a cut or sore.

If hyperglycemia (high blood sugar) goes untreated and remains high for a long-time it can cause toxic acids (ketones) to build up in your blood and urine (ketoacidosis). Signs and symptoms include:

• Nausea and vomiting
• Shortness of breath
• Dry mouth
• Fruity-smelling breath
• Weakness
• Abdominal pain
• Confusion
• Coma

If you have any of these symptoms it is important to get prompt medication attention.

What Can Cause High Blood Sugar?

Now that we are familiar with the basics of how the body uses glucose and signs that you may have high blood sugar, let’s take a look at what can cause your blood sugar levels to creep above the normal range. Yes, your plate full of pasta and breadsticks may be to blame but some of these other reasons may explain why even if your diet is perfect you’re struggling to control your blood sugar levels.

1. Diabetes Medication. If your dose of medication is too low or you are missing doses your blood sugar levels may not be well-controlled. It is important to make sure you are taking the proper medication and amount at the right time. If your blood sugars are running high consistently you may need to have your medications changed or adjusted. If you’re on insulin, double-check with your healthcare team that you are injecting the medication properly and that your insulin is not expired.
2. Food Choices. Carbohydrates are broken down into glucose in the body, if you eat too large of portions or the wrong types of carbohydrates this could lead to high blood sugar.
   1. Poor food choices may be the culprit. There are two types of carbohydrates, simple and complex. Simple carbohydrates are foods that have higher amounts of added sugars and lower fiber. Oftentimes these foods have quick sugar that is easily absorbed into the bloodstream causing a quick blood sugar rise. Examples of simple carbohydrates would be sugar-sweetened beverages, table sugar, baked goods, and breakfast cereals. Complex carbs on the other hand are higher in fiber and are digested more slowly making these types of carbohydrates better for people with diabetes because they help manage blood sugar spikes, promote a healthy weight, and help prevent overeating.
   2. Monitoring portions of carbohydrate foods is important for controlling blood sugars following a meal or snack. If you consume too many carbohydrates at one time you may be overwhelming your body with glucose and make it hard for your insulin to keep up. One serving of carbohydrates is 15 grams of carbohydrates on the nutrient facts panel. Most adults aim for 45-75 grams of carbohydrates per meal, depending on their sex, size, medications, and activity level.
3. Lack of physical activity. Exercise is one of the only ways to a high blood sugar other than medications. If your blood sugar is running high, going on a walk or bike ride will use up the extra glucose as fuel, naturally lowering your numbers. If you are not engaging in physical activity your blood sugars may rise as you are not burning off any of this extra glucose. If you were an active person and then due to an injury or illness, suddenly stopped exercising, you may notice a rise in your readings. Finding time for exercise is an important part of your diabetes management.
4. Illness and stress. Hormones produced to combat illness and stress can lead to increased blood sugars. Even people without diabetes can experience high blood sugars, known as transient hyperglycemia, during times of severe illness. It’s important to evaluate your medications, add stress-management and self-care to your routines, and pay close attention to diet during times of high stress and illness. This may include illness, like the flu or COVID-19, having a bad injury, and recent surgery. Work with your healthcare team to determine what changes may work best for you and ask if you may need to check your blood sugars more frequently until you’re feeling better.
5. Other medications, such as steroids. Steroids can be prescribed for a variety of reasons including injury, pain, lung conditions, and certain infections including COVID-19. A known side effect of steroids is high blood sugar. This is because steroids increase insulin resistance causing your body’s own insulin or injected insulin to not work as well. Many people worry that this elevated blood sugar level is from the food they are eating, but it is most likely from the steroid. Other medications that increase blood sugars include anxiety and depression medications, birth control pills, beta-blockers and thiazide diuretics, high doses of asthma medications, statins, and adrenaline for severe allergic reactions. 

Health Risks of High Blood Sugar

Even if you have a really healthy lifestyle, high blood sugars may still occur from time to time. Keeping your blood sugars in range as much as you can is the best way to reduce your risk for complications and feel your best. If high blood sugar is not addressed, over time it can lead to serious health conditions. Health risks of high blood sugar include:

• Increased risk of heart disease and stroke
• Neuropathy (nerve damage)
• Vision problems, such as diabetic retinopathy or blindness, glaucoma, and cataracts
• Kidney disease or failure
• Dental problems, including infections
• Serious skin infections, ulcers, and in severe cases amputations
• Hearing loss
• Mental health issues, such as depression
• Dementia

Bringing blood sugar levels down to the normal range will eliminate all of the short-term symptoms of high blood sugar and greatly reduce your risk for developing serious health conditions. When taking steps to lower your blood sugar it is important to check your levels frequently and be aware of low blood sugar. Hypoglycemia, or low blood glucose, can lead to a medical emergency as well.

When the body doesn’t have enough sugar to use as fuel, blood sugar levels can drop below 70. This drop can happen because of changes in your diet, medication, and physical activity. Most people will notice symptoms when their blood sugar levels are less than 70 while others may be unaware that they are dangerously low.

Signs of Low Blood Sugar

The following are signs that your blood sugar might be dangerously low:

• Shakiness or trembling
• Hunger
• Headache
• Irritability
• Confusion
• Dizziness
• Sweating
• Anxiety
• Weakness

Some people who are used to their blood sugars running very high may experience some of these symptoms when their blood sugars are still in the normal range. This happens when the body gets accustomed to higher blood sugars and perceives normal levels as too low. If this happens to you, be patient and as your body adjusts to normal or lower blood sugars, these symptoms will fade away.

Not treating a low blood sugar can lead to dangerously low glucose in the blood leading to passing out, seizures, or a coma. If you have any symptoms it is important to check your blood sugar and treat it by consuming some carbohydrates or taking glucose tablets or gel to bring your blood sugars back up as quickly as possible.

What Can Cause Low Blood Sugar?

Low blood sugar is often related to changes in your eating, exercise, medications, or weight. Let’s dig into the reasons why your blood sugar may be going low:

1. Diet changes. Timing of meals and snacks and portions can lead to low blood sugar. If you are significantly reducing the amount of carbohydrates that you are eating, you could be setting yourself up for hypoglycemia. Your body relies on a steady supply of carbohydrates to provide fuel throughout the day, when carbohydrates are restricted the glucose available drops leading to possible low blood sugars. Skipping meals and snacks or waiting too long to eat is another culprit. Staying on a regular eating schedule and eating enough protein and complex carbohydrates will help you avoid a blood sugar rollercoaster ride.

Drinking alcohol on an empty stomach can also cause blood concentrations of glucose to be decreased too. If you plan on having an alcoholic drink, it is best to have it with a meal or snack to help keep blood sugars steady.

If you are on insulin and accidentally dose too much insulin for the amount of carbohydrate you eat or drink, you will likely end up low and need to be ready to treat it.

2. Increased exercise. If you are exercising more than usual, you may burn up extra glucose leading to hypoglycemia. It is often recommended to bring a snack or glucose tablets when exercising or hiking in case you experience this.

3. Changes in medications. Diabetes medications are intended to bring blood sugars down but some types may have a higher risk for low blood sugars than others. Older types of sulfonylureas tend to cause low blood sugar more often than some of the newer ones. If your dose is too high or if you’ve recently lost weight you may need adjustments to your medications to help keep your blood sugar within the normal range.

As with all things in life, balance is key. Keeping blood sugars within normal range with a healthy balance of exercise, nourishing food choices, appropriate medication management, and having proper follow-up with your medical team will help you avoid the ups and downs and keep you in control. You hold the keys to your managing your blood sugar in your hands with the choices you make every day. Start today and let us help you!

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