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What can Cause a Sudden Blood Sugar Drop?

By Erin J. Hill
Updated Mar 03, 2024
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There are a variety of factors which can cause a sudden blood sugar drop to occur, including eating the wrong combination of foods, exercising too strenuously without eating enough, taking certain herbal supplements or medications, and dining on the wrong kind of sugars and carbohydrates. Those with Type 1 diabetes are more likely to experience sudden blood sugar changes, but anyone can suffer from an occasional episode unless steps are taken to prevent it. Most sudden drops in blood glucose levels in non-diabetics stem from improper diet and too much physical activity.

Those with Type 1 diabetes or hypoglycemia are the most at risk for a sudden blood sugar drop. This can be caused by not properly monitoring food intake and combining the wrong foods for proper blood glucose control. For instance, eating refined carbohydrates leads to a rapid increase in blood sugar. This spike is generally followed by a dramatic drop in glucose levels shortly after. Some studies have shown that combining refined carbohydrates or sweets with protein may also exacerbate low blood sugar because the added protein affects the way the body absorbs and processes glucose.

Exercising may also cause a sudden blood sugar drop, primarily if being done on an empty stomach. When the body is engaging in strenuous activity, the heart pumps faster and moves more blood through the body in less time. This increased blood flow can dilute insulin levels and impact how well the body breaks down glucose in foods. If nothing was eaten prior to a workout, glucose levels can drop even further because there is no sugar for the body to break down at all.

Some studies have also shown that certain dietary supplements or foods can cause a sudden drop in blood sugar in some individuals. Green tea, for instance, has lowered blood sugar in several animal studies. It is thought this happens because the polyphenols found in the tea impact the efficiency of insulin. It requires several servings per day to cause a problem with most individuals, and green tea should not necessarily be avoided since it offers many health benefits. Those with Type 1 diabetes should consult a health care professional before drinking green tea, however, and it should not be consumed on an empty stomach.

In some cases, a sudden blood sugar drop may occur in those with type-2 diabetes who are taking insulin or another blood glucose lowering medication. This generally happens when the medications are taken in higher dosages than recommended, or when the drugs are taken without proper food intake. It is very important for all diabetics to carefully monitor blood sugar levels to ensure that they are normal both before and after meals.

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Discussion Comments

By anon1000882 — On Jan 19, 2019

I have type 2 diabetes as a result of herbicide poisoning (agent orange) and have experienced two types of glucose crashes. The first is when the insulin injection goes IV. Two clues: blood in the syringe and blood at the injection site. The crash will occur within two hours if in fact the injection did go IV. The second is a crash during sleep period between 3 and 5 AM. This for me occurs 1 to 3 times a month with the glucose dropping sometimes as low as the 30s. To this I respond with an intake of 50 to 80 carbs as I fall into a very deep sleep. This has been on going for the last 30 years and was much worse when taking pills.

By anon998764 — On Aug 20, 2017

About an hour before one of my main meals I feel irritable and frustrated. I eat some crackers with peanut butter until I get home. If I interact with someone, they judge me as being rude.

This is difficult and I have to make sure I'm not in public during this time, but sometimes it's unavoidable. Such as being stopped by the police and trying to say that I must get home to cook my meal, but they insist on calling an ambulance. No.

By anon927839 — On Jan 26, 2014

I am a type 2 and never experienced sudden drops (or even hypoglycemia) until a few weeks ago. Now my blood sugars seem to be all over the place. This afternoon, my bg level dropped by 100 in just 90 minutes. I think it's due to medications I am taking, but am not sure because it happens at different times and I've not been able to identify a pattern. It greatly concerns me and I will continue to work with my endocrinologist to figure it out.

By SarahGen — On Jan 10, 2014

I've only had low blood sugar symptoms twice in my life. Both times, it was summer and I was working outdoors. Heat and exhaustion seem to cause my blood sugar to drop. My blood pressure falls at the same time.

By discographer — On Jan 10, 2014

@donasmrs-- Do you check your blood sugar regularly with your monitor? You might want to jot down blood sugar levels at morning, noon and evening in a notebook. This might give you an idea of how your blood sugar fluctuates during the day.

Also, when your blood sugar drops or rises suddenly, make note of your blood sugar levels and what you did before. You can take these notes to your doctor to figure out what's causing your low blood sugar levels. An adjustment in your medication dose and time, diet or exercise may be necessary.

I experience blood sugar drops sometimes too but it usually happens when I eat too little and take too much anti-diabetic medication. I always keep some glucose tables with me for emergencies.

By donasmrs — On Jan 09, 2014

I have type 2 diabetes and my blood sugar drops sometimes. I have no idea what's causing it though. I haven't noticed any triggers. I do the same things every day. I take the same dose of medication and eat the same, healthy food.

Are there any other type 2 diabetics here? Does your sugar fall suddenly sometimes? Do you know what's causing it?

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