Why Does My Blood Sugar Fluctuate So Much? Causes

Medically Reviewed on 5/26/2022
Why Does My Blood Sugar Fluctuate So Much
Learn about can cause your blood sugar to fluctuate and how you can keep your glucose levels under control

Whether you were just diagnosed with type 2 diabetes or have been living with it for some time, you are probably aware of how volatile blood sugar levels can be and how critical it is to keep them under control. 

According to the National Institutes of Health (NIH), proper blood sugar control is critical for avoiding potential diabetic complications such as kidney disease, nerve damage, eye issues, stroke, and heart disease. However, managing all the factors that can affect blood sugar can be very difficult. 

Even if you keep an eye on what you eat and take medications as prescribed, you will likely see your blood sugar fluctuate due to some factors beyond your control.

What can cause blood sugar fluctuations?

Factors that can increase blood glucose levels (hyperglycemia) include:

Factors that can lower blood glucose levels (hypoglycemia) include:

  • Protein-rich foods
  • Vegan diet
  • Skipping meals
  • Fasting
  • Increasing physical activity without eating more or adjusting your medications
  • Taking too much insulin or diabetes medication
  • Drinking alcohol

How can you stop the blood sugar rollercoaster?

If your blood sugar levels swing from too high to too low (and vice versa) like a rollercoaster, you will have to monitor your glucose levels before and after meals and activities to determine what is causing the fluctuations.

Factors that impact blood sugar levels include:

  • What you eat
  • How long ago you ate
  • Initial blood glucose level
  • Physical activity
  • Stress
  • Sickness 
  • Sleep habits

When you use insulin to treat high blood sugar, you risk overcompensating and having low blood sugar after 1-2 hours. When you have low blood sugar, it is easy to overeat and wind up causing a spike again. Such fluctuations can make you feel sluggish and are harmful to your long-term health.

A blood sugar rollercoaster can be caused by the following:

  • Avoid refined carbs: When you are diagnosed with diabetes, you may find it difficult to make huge changes in your eating pattern. Additionally, you may not be aware of the dramatic blood sugar spikes that refined carbs can cause. If you want to get off the rollercoaster, you need to limit eating and drinking foods with refined sugars and grains. Mixing fiber-rich foods such as chia seeds with these foods may also help keep your blood sugar in control.
  • Watch your physical activity: Your body reacts differently to different types of physical activity, especially during various times of day. It is not uncommon to notice a minor increase in blood glucose if you exercise first thing in the morning, even though the same amount of activity later in the day can cause reduction in blood glucose levels. Exercise can also be challenging as it can cause rapid changes in blood sugar levels in some people while helping to even out the extremes in others. The goal is to monitor your own reactions to exercise and figure out what levels of activity and when affect your blood glucose levels.
  • Reduce stress: Stress, whether mental or physical, can trigger your body to release glucose-raising chemicals such as adrenaline. When you are anxious or unhappy, more cortisol circulates in your bloodstream, making your muscles more resistant to insulin. Sickness or infection can also cause blood sugar spikes. Finding ways to de-stress can help you prevent blood sugar fluctuations.


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What is hypoglycemia?

Hypoglycemia occurs when blood glucose levels fall below 4 mmol/L (72 mg/dL). However, some individuals may experience hypoglycemic symptoms even at blood sugar levels of 75 mg/dL.

While many think of diabetes as a condition characterized by high blood sugar levels, sometimes people with diabetes take medications that can cause their blood sugar levels to drop too low, which can be deadly.

Understanding the early signs of hypoglycemia can help you keep your blood glucose levels under control.

Symptoms of hypoglycemia

Causes of hypoglycemia

While medication is the most common cause of hypoglycemia in people with diabetes, a variety of other factors can increase the risk of the condition:

  • Pharmaceutical dosage that is too high (insulin or hypo causing tablets)
  • Delayed meals
  • Intermittent fasting
  • Exercise 
  • Alcohol

Treatment of hypoglycemia

Minor cases of hypoglycemia can be treated with 15-20 g of fast-acting carbs, such as glucose tablets, candy, or fruit juice.

A blood test should be performed after 15-20 minutes to determine whether blood glucose levels have returned to normal. Severe hypoglycemia may require immediate medical attention, for example, if you lose consciousness or have a seizure that lasts longer than 5 minutes.

What is hyperglycemia?

Hyperglycemia occurs when people with diabetes have an abnormally high level of sugar in their system. The World Health Organization defines it as:

  • Levels of blood glucose more than 7.0 mmol/L (126 mg/dL) while fasting
  • Levels of blood glucose more than 11.0 mmol/L (200 mg/dL) 2 hours after eating

Symptoms of hyperglycemia

Causes of hyperglycemia

The underlying cause of hyperglycemia is typically the loss of insulin-producing cells in the pancreas or insulin resistance. Immediate causes of hyperglycemia include:

  • Missing a diabetes medication dosage 
  • Consuming more carbs than your body and/or medicine can handle
  • Mental or emotional stress (anxiety, injury, surgery)
  • Infection

Complications of hypoglycemia

Hyperglycemia can be dangerous and cause life-threatening complications:

  • Diabetic ketoacidosis:
    • Ketoacidosis is a potentially fatal condition that mostly affects patients with type 1 diabetes but can also affect certain persons with type 2 diabetes who are insulin dependent. If blood glucose levels climb beyond 15 mmol/L (270 mg/dL), the risk of ketoacidosis increases significantly.
    • If an insulin dosage is missed or if you are sick, you are more likely to develop ketoacidosis.
    • If blood glucose levels remain exceedingly high, above 33 mmol/L (600 mg/dL) for a lengthy period, a complication known as hyperosmolar hyperglycemic nonketotic syndrome can occur.
  • Organ damage:
    • Having high blood glucose levels for longer periods of time raises the risk of permanent damage to the eyes, nerves, kidneys, and blood vessels, which can lead to long-term consequences of diabetes.
    • Maintaining a HbA1c level of 48 mmol/mol (6.5 percent) or lower will reduce the chances of acquiring diabetic complications.

Treatment of hyperglycemia

If you have diabetes and are experiencing symptoms of hyperglycemia, follow the recommendations given to you by your care team to lower your blood sugar levels.

It is possible that you will be instructed to:

  • Avoid foods that raise your blood sugar levels, such as sugary beverages
  • Increase fluid intake and switch to sugar-free drinks
  • Exercise more frequently
  • Adjust insulin dosage as per required

You may also be recommended to keep a closer eye on your blood sugar levels or to have your blood or urine tested for ketones (which are associated with diabetic ketoacidosis).

Until your blood sugar levels return to normal, keep an eye out for any other symptoms that may indicate a more serious problem.

Medically Reviewed on 5/26/2022
Image Source: iStock Image

20 Reasons for Blood Sugar Swings: https://www.webmd.com/diabetes/ss/slideshow-blood-sugar-swings

Hyperglycemia and hypoglycemia in type 2 diabetes: https://www.ncbi.nlm.nih.gov/books/NBK279510/

10 surprising Things That Can Spike Your Blood Sugar: https://www.cdc.gov/diabetes/library/spotlights/blood-sugar.html