Blood Sugar Health
Understanding why blood sugar drops
Published: Jan. 23, 2026
Updated: Jan. 26, 2026
8 min read
Dealing with low blood sugar, or hypoglycemia, is one of the most challenging aspects of managing diabetes. Experiencing lows isn’t just frustrating, it can also feel stressful and even scary. Diabetes is a complex condition, and it’s not always easy to know what causes lows when they happen. Learning more about why blood sugar drops can help you identify what might be behind lows and empower you to get ahead of serious low blood sugar, especially if you experience hypoglycemia unawareness. Understanding the factors that contribute to hypoglycemia is an important part of learning to manage diabetes. Knowing what causes lows can help you work to prevent them before they happen, giving you a greater sense of control around managing your blood sugar.
Common Reasons Why Blood Sugar Drops
There are many factors that affect blood sugar, or glucose, levels beyond just diet and exercise. The diaTribe Foundation has identified at least 42 factors that can contribute to changes in blood sugar.1 It’s important to understand that every body is unique. Circumstances or choices that might cause lows in one person may not have the same effect on someone else.
The body, and the factors that affect glucose, also shift from day to day. Something that led to a low one day may not cause lows on another. Additionally, the things that can impact blood sugar may change as you age. Using a continuous glucose monitoring (CGM) system like the Dexcom G7 CGM System can help you track patterns in your glucose, which can make it a little easier to identify why you experience low glucose. You and your healthcare provider can work together to keep an eye on what tends to cause lows for you and make adjustments to your treatment as you move through your diabetes management journey.
Here are just some of the many reasons why blood sugar drops:
Meals and Meal Timing
Even people who do not live with diabetes can experience low blood sugar when they haven’t eaten enough carbohydrates, or carbs.2 Carbs break down into glucose through digestion. When we don’t eat enough carbs, the body can’t get the glucose it needs to function properly.2,3 Skipping meals or waiting too long between meals throughout the day can contribute to low blood sugar.3 It’s a good idea to find a meal schedule that you can stick to and ensure that you’re eating balanced meals or snacks with enough carbs as well as other important nutrients like fat and protein.2,3,4
Following the diabetes plate method can help you ensure you’re getting a good amount of carbs through your main meals. Fill up half your plate with vegetables or fruits, a quarter with lean protein, and a quarter with carbs.5 It’s also smart to check your food’s glycemic index (GI), which can tell you how much a food will raise your glucose levels.[6] Foods with a high GI, including candy and sugar, as well as simple carbs like white rice, pasta, and pastries, can cause a spike in glucose that may lead to what’s known as reactive hypoglycemia.2,7 While people who have had stomach bypass surgery are more likely to experience reactive hypoglycemia, it may also be one of the reasons why blood sugar drops after eating in those living with diabetes who have not had this type of surgery.2
Can Drinking Alcohol Cause Blood Sugar to Drop?
Drinking alcohol can cause a drop in blood sugar and lead to hypoglycemia. This is because our liver is responsible for processing alcohol and for storing and releasing extra glucose between meals.8 When we consume alcoholic beverages, the liver prioritizes breaking down toxins in alcohol so the body can get rid of them. If the liver is busy managing alcohol, it can’t provide the extra glucose the body might need to avoid low blood sugar.8 Those who use insulin therapy may experience delayed low blood sugar up to 24 hours after drinking.9
Insulin Doses
For individuals living with T1D or T2D using insulin therapy, eating enough carbs goes hand-in-hand with calculating insulin doses. Insulin is a hormone that helps our cells absorb glucose from the bloodstream.3 Taking too much insulin compared to the amount of carbs you’ve eaten or how much physical activity you’ve done might be one of the reasons why blood sugar drops suddenly.3 Using insulin that has expired or hasn’t been stored properly can also lead to an unexpected low after taking it.10
There are a few types of insulin that serve different purposes, including rapid- or short-acting insulin that is typically taken around mealtimes and long-acting insulin that keeps glucose levels stable throughout the day.11 It’s important to talk to your doctor about how and when to use each type of insulin to ensure that you’re giving yourself the right amount at the right time. Balancing insulin doses and glucose can be especially challenging at night because of the long span of time between meals. Dosing too much insulin or not eating enough before bed can lead to a low while you sleep, also known as nighttime hypoglycemia.10
Using Dexcom CGM Systems, including Dexcom G7, can provide real-time glucose readings that can help you calculate your insulin doses. Dexcom G7 also integrates with compatible insulin pumps to provide automated insulin delivery (AID), making dosing insulin a little easier.* To help you get ahead of hypoglycemia, Dexcom CGM Systems have a predictive alert that can let you know up to 20 minutes before you’re likely to experience a low under 3.1 mmol/L, giving you time to take action to prevent lows before they happen.† This can help you see if you’re headed for a low between meals or when you’re asleep.
Interactions with Glucose-Lowering Medications
Individuals living with T2D may take glucose-lowering medications such as metformin, sulfonylureas, or GLP-1 agonists like Trulicity®, Ozempic®, and Mounjaro® to manage their blood sugar levels.12 These types of medications can be effective diabetes treatments that lead to an improvement in A1C over time and they aren’t likely to cause hypoglycemia when taken as advised.
However, taking too much medication or combining these medications with certain non-diabetes-related medications or herbal supplements may lead to an unexpected drop in blood sugar.13,14 Medications, like birth control as well as hormone replacement therapy (HRT), can also change the way diabetes medications work in the body.14 Those who use glucose-lowering medications alongside insulin therapy also need to be aware of how their insulin doses interact with their medication routine.12,14
It’s important to talk to your doctor about any other medications or treatments you’re using alongside glucose-lowering medication. They can provide insight on which options might interact with your medication and cause low blood sugar.
Exercise and Everyday Physical Activity
In general, physical activity is a great way to manage glucose levels and reduce A1C.15 Intense physical activity and exercise can lower glucose immediately and potentially lead to hypoglycemia.16 Why do blood sugar levels drop after exercise? When we’re physically active, the cells in our muscles become more sensitive to insulin, allowing them to absorb glucose more efficiently. When muscles contract during exercise, they can also absorb glucose without needing insulin at all.16 While this can keep your glucose within your ideal range, it may also lead to a rapid drop in blood sugar after you’re done exercising.16
Engaging in physical activity can increase insulin sensitivity and keep glucose levels low for up to 24 hours afterwards.16 Intense exercise—like challenging workouts and sports practices or games—may be more likely to cause hypoglycemia, so it’s important to eat enough carbs and adjust your insulin doses accordingly.15,16 It’s a good idea to talk to your diabetes care team or a certified diabetes educator (CDE) about techniques that can help you manage glucose during workouts.
In addition to formal exercise, everyday physical activities like raking leaves, lugging the vacuum up and down the stairs, running around with kids, deep-cleaning your house, or unloading heavy groceries can also have an impact on glucose levels. You may not always be able to predict what activities will cause lows, which is why it’s important to keep snacks or quick sources of glucose with you, such as juice or candy, to treat hypoglycemia.17
The Menstrual Cycle and Menopause
For those who experience menstruation, hormonal shifts that happen through their monthly cycles and before and during menopause can contribute to fluctuations in blood sugar.
Individuals who menstruate and are not on hormonal birth control might find that their glucose levels are lower or more stable during the time between finishing their period and ovulation.18,19 Hormonal changes that happen after you ovulate and before you get your period again can lead to a reduction in insulin sensitivity, resulting in higher glucose levels just before and for the first couple of days of your period.18,19 If you’re using insulin therapy, experiencing higher blood sugar levels might prompt you to give yourself more insulin than usual. This change in your insulin routine may increase the likelihood of experiencing low blood sugar, especially after you exercise and while you sleep.18,19
Through perimenopause and menopause, major hormones, including estrogen and progesterone, start to decrease, which leads to changes in the way the body regulates glucose.20 If you’re experiencing hormonal changes, you may notice that your blood sugar rises and drops unexpectedly. Menopause can also cause weight gain, which can affect the way diabetes medications work.20 It’s a good idea to talk to your healthcare team about adjusting your diabetes management plan to support you through menopause.
Getting Ahead of Low Glucose with Dexcom G7
Dexcom G7 can give you and your diabetes care team more insight into what might be causing low glucose. Using Dexcom G7 allows you to see your glucose readings in the palm of your hand, on your compatible smartphone, smartwatch, or receiver, without the need for routine fingersticks.‡§ You can easily log your activities, meals, and any other factors that might affect your glucose in the Dexcom G7 app, giving you a better idea of what’s leading to lows.
You and your doctor can also use Dexcom Clarity to see days, weeks, or months’ worth of glucose data so that you can spot patterns in your readings and identify what habits or treatments might be contributing to hypoglycemia.|| With more data, you and your team can make informed changes to your diabetes management routine and help you avoid low glucose in the future.
* Not all connections are available in Canada. To learn more about insulin pump integrations and compatibility with Dexcom CGM Systems, visit dexcom.com/en-ca/partnerships/integrations-and-compatibility.
† Provides a warning up to 20 minutes in advance of severe hypoglycemia (glucose levels at or below 3.1 mmol/L).
‡ For a list of compatible smart devices, please visit www.dexcom.com/compatibility.
§ If your glucose alerts and readings do not match symptoms or expectations, use a blood glucose meter to make diabetes treatment decisions.
|| An internet connection is required to send data to Dexcom Clarity.
† Provides a warning up to 20 minutes in advance of severe hypoglycemia (glucose levels at or below 3.1 mmol/L).
‡ For a list of compatible smart devices, please visit www.dexcom.com/compatibility.
§ If your glucose alerts and readings do not match symptoms or expectations, use a blood glucose meter to make diabetes treatment decisions.
|| An internet connection is required to send data to Dexcom Clarity.
1 Brown A. 42 Factors That Affect Blood Glucose?! A Surprising Update. The diaTribe Foundation. Updated September 29, 2022. Accessed November 8, 2024. https://diatribe.org/diabetes-management/42-factors-affect-blood-glucose-surprising-update
2 Hypoglycemia. Mayo Clinic. Updated November 18, 2023. Accessed November 8, 2024. https://www.mayoclinic.org/diseases-conditions/hypoglycemia/symptoms-causes/syc-20373685
3 Diabetic hypoglycemia. Mayo Clinic. May 6, 2022. Accessed November 8, 2024. https://www.mayoclinic.org/diseases-conditions/diabetic-hypoglycemia/symptoms-causes/syc-20371525
4 Hypoglycemia (Low Blood Sugar). Cleveland Clinic. Reviewed January 31, 2023. Accessed November 8, 2024. https://my.clevelandclinic.org/health/diseases/11647-hypoglycemia-low-blood-sugar
5 Healthy eating: your path to better management. Diabetes Canada. Accessed November 8, 2024. https://diabetes.ca/nutrition-fitness/healthy-eating/healthy-eating-tips
6 Understanding the glycemic index (GI). Diabetes Canada. Accessed November 8, 2024. inhttps://www.diabetes.ca/resources/tools-resources/understanding-the-glycemic-index-(gi)
7 Reactive Hypoglycemia – Hypos After Eating. Diabetes.co.uk. Updated October 29,2023. Accessed November 8, 2024. https://www.diabetes.co.uk/reactive-hypoglycemia.html
8 Alcohol and Diabetes. American Diabetes Association. Accessed November 8, 2024. https://diabetes.org/health-wellness/alcohol-and-diabetes
9 Alcohol and diabetes. Diabetes Canada. April 2018. Accessed November 8, 2024. https://www.diabetes.ca/DiabetesCanadaWebsite/media/Managing-My-Diabetes/Tools%20and%20Resources/alcohol-and-diabetes.pdf?ext=.pdf
10 Nocturnal Hypoglycemia. MyHealth Alberta. Updated July 28, 2021. Accessed November 8, 2024. https://myhealth.alberta.ca/Health/pages/conditions.aspx?hwid=uq2844&
11 Types of Insulin. HealthLink BC. Updated March 1, 2023. Accessed November 8, 2024. https://www.healthlinkbc.ca/health-topics/types-insulin
12 Lipscombe L, et al. Diabetes Canada 2018 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Pharmacologic Glycemic Management of Type 2 Diabetes in Adults: 2020 Update. Can J Diabetes. 2020;44(7):575-591. doi:10.1016/j.jcjd.2020.08.001
13 Gupta RC, et al. Interactions between antidiabetic drugs and herbs: an overview of mechanisms of action and clinical implications. Diabetol Metab Syndr. 2017;9:59. Published 2017 Jul 26. doi:10.1186/s13098-017-0254-9
14 Taking metformin with other medicines and herbal supplements. NHS. Reviewed March 24, 2022. Accessed November 8, 2024. https://www.nhs.uk/medicines/metformin/taking-metformin-with-other-medicines-and-herbal-supplements/
15 Sigal RJ, et al. Diabetes Canada 2018 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Physical Activity and Diabetes. Can J Diabetes. 2018;42 Suppl 1:S54-S63. doi:10.1016/j.jcjd.2017.10.008
16 Blood Glucose and Exercise. American Diabetes Association. Accessed November 8, 2024. https://diabetes.org/health-wellness/fitness/blood-glucose-and-exercise
17 Lega IC, et al. Diabetes Canada 2018 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Hypoglycemia in Adults. Can J Diabetes. 2023;47(7):548-559. doi:10.1016/j.jcjd.2023.08.003
18 Toor S, et al. Type 1 Diabetes and the Menstrual Cycle: Where/How Does Exercise Fit in?. Int J Environ Res Public Health. 2023;20(4):2772. Published 2023 Feb 4. doi:10.3390/ijerph20042772
19 Zeinab M, et al. Effect of Menstrual Cycle on Glycemic Responses to Exercise in Female Participants with Type 1 Diabetes. Diabetes. 2022; 71 (Supplement_1): 243–OR. https://doi.org/10.2337/db22-243-OR
20 Kelly L. Menopause: The change that can add challenges to diabetes management. Mayo Clinic Press. May 24, 2022. Accessed November 8, 2024. https://mcpress.mayoclinic.org/diabetes/menopause-the-change-that-can-add-challenges-to-diabetes-management/
2 Hypoglycemia. Mayo Clinic. Updated November 18, 2023. Accessed November 8, 2024. https://www.mayoclinic.org/diseases-conditions/hypoglycemia/symptoms-causes/syc-20373685
3 Diabetic hypoglycemia. Mayo Clinic. May 6, 2022. Accessed November 8, 2024. https://www.mayoclinic.org/diseases-conditions/diabetic-hypoglycemia/symptoms-causes/syc-20371525
4 Hypoglycemia (Low Blood Sugar). Cleveland Clinic. Reviewed January 31, 2023. Accessed November 8, 2024. https://my.clevelandclinic.org/health/diseases/11647-hypoglycemia-low-blood-sugar
5 Healthy eating: your path to better management. Diabetes Canada. Accessed November 8, 2024. https://diabetes.ca/nutrition-fitness/healthy-eating/healthy-eating-tips
6 Understanding the glycemic index (GI). Diabetes Canada. Accessed November 8, 2024. inhttps://www.diabetes.ca/resources/tools-resources/understanding-the-glycemic-index-(gi)
7 Reactive Hypoglycemia – Hypos After Eating. Diabetes.co.uk. Updated October 29,2023. Accessed November 8, 2024. https://www.diabetes.co.uk/reactive-hypoglycemia.html
8 Alcohol and Diabetes. American Diabetes Association. Accessed November 8, 2024. https://diabetes.org/health-wellness/alcohol-and-diabetes
9 Alcohol and diabetes. Diabetes Canada. April 2018. Accessed November 8, 2024. https://www.diabetes.ca/DiabetesCanadaWebsite/media/Managing-My-Diabetes/Tools%20and%20Resources/alcohol-and-diabetes.pdf?ext=.pdf
10 Nocturnal Hypoglycemia. MyHealth Alberta. Updated July 28, 2021. Accessed November 8, 2024. https://myhealth.alberta.ca/Health/pages/conditions.aspx?hwid=uq2844&
11 Types of Insulin. HealthLink BC. Updated March 1, 2023. Accessed November 8, 2024. https://www.healthlinkbc.ca/health-topics/types-insulin
12 Lipscombe L, et al. Diabetes Canada 2018 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Pharmacologic Glycemic Management of Type 2 Diabetes in Adults: 2020 Update. Can J Diabetes. 2020;44(7):575-591. doi:10.1016/j.jcjd.2020.08.001
13 Gupta RC, et al. Interactions between antidiabetic drugs and herbs: an overview of mechanisms of action and clinical implications. Diabetol Metab Syndr. 2017;9:59. Published 2017 Jul 26. doi:10.1186/s13098-017-0254-9
14 Taking metformin with other medicines and herbal supplements. NHS. Reviewed March 24, 2022. Accessed November 8, 2024. https://www.nhs.uk/medicines/metformin/taking-metformin-with-other-medicines-and-herbal-supplements/
15 Sigal RJ, et al. Diabetes Canada 2018 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Physical Activity and Diabetes. Can J Diabetes. 2018;42 Suppl 1:S54-S63. doi:10.1016/j.jcjd.2017.10.008
16 Blood Glucose and Exercise. American Diabetes Association. Accessed November 8, 2024. https://diabetes.org/health-wellness/fitness/blood-glucose-and-exercise
17 Lega IC, et al. Diabetes Canada 2018 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Hypoglycemia in Adults. Can J Diabetes. 2023;47(7):548-559. doi:10.1016/j.jcjd.2023.08.003
18 Toor S, et al. Type 1 Diabetes and the Menstrual Cycle: Where/How Does Exercise Fit in?. Int J Environ Res Public Health. 2023;20(4):2772. Published 2023 Feb 4. doi:10.3390/ijerph20042772
19 Zeinab M, et al. Effect of Menstrual Cycle on Glycemic Responses to Exercise in Female Participants with Type 1 Diabetes. Diabetes. 2022; 71 (Supplement_1): 243–OR. https://doi.org/10.2337/db22-243-OR
20 Kelly L. Menopause: The change that can add challenges to diabetes management. Mayo Clinic Press. May 24, 2022. Accessed November 8, 2024. https://mcpress.mayoclinic.org/diabetes/menopause-the-change-that-can-add-challenges-to-diabetes-management/