Published 27th July 2023

What’s the connection between low blood sugar and headaches?

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If you think your headache is related to low blood sugar or feeling hungry, you might be right. Research shows that low blood sugar can cause headaches or make them worse.

Low blood sugar, or hypoglycemia, is when your blood sugar drops below a healthy level. You're most likely to experience this if you have diabetes. It’s especially likely if you take too much insulin.

How low is too low? There’s some variation from person to person.

If you have diabetes, doctors consider it to mean that the level of glucose (sugar) in your blood is under 70 milligrams per deciliter (mg/dL) or 4 millimoles per liter (mmol/L).

Hypoglycemia is rare in people without diabetes. But it's still possible to experience headaches and other symptoms if your blood sugar level falls too rapidly.

You can treat hypoglycemia-induced headaches with over-the-counter painkillers and by eating the right foods.

At ZOE, we run the world's largest nutrition science study, and our data show that everyone responds to foods differently. 

You can learn more about how your blood sugar levels respond to different foods with our at-home test. Our personalized nutrition program can then help you choose the best foods for your body. 

Learn more about how it works by taking our free quiz.

Can low blood sugar cause headaches? 

Yes, low blood glucose can cause headaches, though we still don't know exactly why.

You're more likely to experience low blood sugar headaches if you have diabetes. These factors can all cause low blood sugar:

  • taking too much insulin

  • taking it at the wrong time

  • skipping or delaying meals

  • not eating enough carbs

  • drinking too much alcohol

  • exercising too intensely

You can also get a headache and other hypoglycemia symptoms if your blood sugar falls too rapidly or dips lower than normal — even if it's still in the normal range. 

For someone without diabetes to get a low blood sugar headache, their blood sugar would usually need to fall as low as 55 mg/dL or 3 mmol/L.

These headaches can happen if you've had gastric bypass surgery, are pregnant, or have certain health conditions

They can also occur if you fast for too long, or if you have a very high-carb meal, which can trigger the release of too much insulin. This is the hormone that helps regulate your blood sugar levels.

Relationship with migraine

Migraine is a common condition. Typically, the main symptom is recurrent, throbbing head pain, usually on one side.

Scientists think that low blood sugar may trigger migraine headaches. Research shows that missing a meal is a trigger for many people with the condition.

A rapid change in glucose levels can lead to a stress response in your body, and this could prompt a migraine headache.

If you keep getting these headaches, it may be because the cells in your brain aren’t responding to insulin as they should. However, we need more research to confirm this.

A possible clue that your migraine headache is related to low blood sugar is if you crave carbs just before the pain strikes. The craving may be your body's way of trying to regulate your blood sugar.

Editor’s summary

Low blood sugar (hypoglycemia) can cause headaches, and it’s more common in people with diabetes.

Hypoglycemia can result from using too much insulin, missing meals, drinking too much alcohol, or doing too much strenuous exercise.

If you don’t have diabetes, these headaches can stem from rapid blood sugar drops or certain triggers, such as pregnancy, prolonged fasting, or high-carb meals.

What does it feel like?

A headache from hypoglycemia typically feels like dull throbbing in your temples.

You’ll often have other symptoms of low blood sugar, too. 

Other symptoms of low blood sugar

In addition to having a headache, you may be:

  • jittery or shaky

  • tired

  • hungry

  • sweaty 

  • dizzy or light-headed

  • irritable, anxious, or moody

You might also have a fast or irregular heartbeat.

Without treatment for hypoglycemia, you may develop more severe symptoms, such as:

  • blurred vision

  • weakness or clumsiness

  • confusion or difficulty concentrating

  • difficulty speaking

  • seizures, or fits

  • collapsing or passing out

Hypoglycemia can be potentially life-threatening if you don’t treat it quickly, especially for people with diabetes.

If you're experiencing severe low blood sugar symptoms, seek medical help.

It’s also worth noting that hypoglycemia is rare if you don’t have diabetes.

Other causes of headaches

Low blood sugar isn't the only cause of a dull, throbbing headache. Similar headaches can stem from:

  • stress

  • dehydration

  • a cold or the flu

These factors can also cause tiredness, shakiness, and light-headedness.

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Below are other causes of headaches, though the pain tends to be different from a low blood sugar headache:

  • bad posture

  • eyesight problems

  • drinking too much alcohol 

  • taking too many painkillers

  • having your period or going through menopause

If your headache keeps returning, or if painkillers aren't helping and it's getting worse, it's important to contact a doctor. 

Diagnosis

If you have diabetes, doctors consider blood glucose levels of 70 mg/dL or 4 mmol/L to be in the hypoglycemic range. 

For people who don’t have diabetes, lower levels of blood sugar don’t typically cause problems until they drop below 55 mg/dL or 3 mmol/L.

A doctor will diagnose hypoglycemia if: 

  1. Your blood sugar level is below 70 mg/dL or 4 mmol/dL (if you have diabetes). 

  2. You're experiencing symptoms of low blood sugar, which may be a headache.

  3. Your symptoms disappear when your blood sugar level returns to normal.

You can typically manage a one-off episode of low blood sugar at home. 

But if you're regularly experiencing symptoms of hypoglycemia (especially if you have diabetes) or if your symptoms are severe, you need help from a doctor. 

Treatment

If you have a headache due to low blood sugar, you can:

It's also a good idea to drink plenty of water in case your headache is related to dehydration.

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

 What to reach for when you have hypoglycemia depends on your situation.

If you have diabetes

If your blood sugar is under 70 mg/dL or 4 mmol/L, follow the 15-15 rule. This means eating 15 grams of quickly digested carbs, such as half a banana or half a cup of orange juice, and testing your levels again 15 minutes later.

Repeat this until your blood glucose is at least 70 mg/dL or 4 mmol/L. 

Only take this approach if your symptoms aren't severe enough to warrant medical attention.

If you don't have diabetes

If your blood sugar is under 55 mg/dL or 3 mmol/L and you have symptoms, you might also want to try the 15-15 approach above.

If you don't have symptoms, eat a well-balanced meal or snack.

A whole-food source of carbs plus protein and healthy fat should be enough to restore your glucose to a normal range.

Prevention

To keep your blood sugar in a healthy range and avoid low blood sugar headaches: 

  • Eat good-quality, whole-food sources of carbs, such as plant foods.

  • Limit sources of ultra-processed carbs, including sodas and other sweetened drinks.

  • Pair carbs with protein and a little healthy fat.

  • Avoid skipping meals and prolonged fasting.

  • Don’t have too much alcohol or sugar, especially on an empty stomach.

Also, sleep problems are a trigger and risk factor for both migraine and insulin resistance

So, finding ways to get enough quality sleep could also help reduce your risk of a low blood sugar headache.

The strategies above will help most people. But there is personal variation when it comes to blood sugar responses.

At ZOE, we know that everyone is unique. With ZOE's at-home test, you can learn how your blood sugar levels respond to the foods you eat. Your personalized nutrition program can help you eat the best foods for your body and long-term health. 

Find out more by taking our free quiz.

What about high blood sugar?

High blood sugar, or hyperglycemia, may also trigger headaches. 

The headaches typically occur after you have a high-carb meal, such as a large bowl of white pasta.

Your body needs more insulin to respond to this food, and you may have a blood sugar dip or crash afterward. 

Avoiding ultra-processed carbs and having well-balanced meals can help prevent headaches from high blood sugar.

Summary

Low blood sugar, or hypoglycemia, can cause headaches. You're more likely to experience this if you have diabetes — hypoglycemia is rare in people without it.

Doctors consider blood sugar to be low when it falls under 70 mg/dL or 4 mmol/L in people with diabetes.

A low blood sugar headache feels like dull throbbing at your temples. It may occur with other symptoms of hypoglycemia, such as feeling hungry, tired, or light-headed.

If you have this type of headache, over-the-counter painkillers can help temporarily.

And eating a source of carbs will help your blood sugar get back into the normal range.

You can help prevent low blood sugar headaches by choosing foods that keep your blood sugar in a healthy range. 

Sources

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Glucose-related traits and risk of migraine: A potential mechanism and treatment consideration. Genes. (2022). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9141901/ 

Headaches. (2021). https://www.nhs.uk/conditions/headaches/ 

Hypoglycemia. (2023). https://headaches.org/hypoglycemia/ 

Hypoglycemia. StatPearls. (2022). https://www.ncbi.nlm.nih.gov/books/NBK534841/ 

Hypoglycemia (low blood glucose). (2023). https://diabetes.org/healthy-living/medication-treatments/blood-glucose-testing-and-control/hypoglycemia 

Hypoglycemia: The neglected complication. Indian Journal of Endocrinology and Metabolism. (2013). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3784865/ 

Insulin resistance & prediabetes. (2018). https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance

Low blood sugar (hypoglycaemia). (2020). https://www.nhs.uk/conditions/low-blood-sugar-hypoglycaemia/ 

Migraine. (2021). https://medlineplus.gov/migraine.html 

Migraine, brain glucose metabolism and the "neuroenergetic" hypothesis: A scoping review. The Journal of Pain. (2022). https://www.jpain.org/article/S1526-5900(22)00039-6/fulltext 

Migraine triggers: An overview of the pharmacology, biochemistry, atmospherics, and their effects on neural networks. Cureus. (2021). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8088284/ 

Non-diabetic hypoglycemia. StatPearls. (2022). https://www.ncbi.nlm.nih.gov/books/NBK573079/ 

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