Can I Get a Headache After Eating Sugar or Fasting from Sugar?

A sugar headache can occur when blood sugar is too high, like after eating too much candy. Hormones are affected in a way that narrows blood vessels in the brain, causing pain. Similarly, too-low blood sugar—which can occur when skipping meals—can trigger hormones to dilate these vessels, causing sugar withdrawal headaches.

These headaches commonly affect individuals with diabetes, but can also occur in people without the condition.

Regulating your blood sugar can help prevent these and other symptoms. However, if you have severe or long-lasting sugar-related headaches, be sure to talk to your healthcare provider.

Hypoglycemia 

Fluctuations in sugar levels cause changes in hormone levels. Specific hormones that can be affected include epinephrine and norepinephrine. These changes cause the blood vessels in the brain to dilate. Headaches that occur due to hypoglycemia are often described as a dull, throbbing pain at the temples.

Migraines can also be triggered by hypoglycemia. They present with severe and throbbing pain that typically occurs on one side of the head. Those with hypoglycemia-induced migraines tend to only experience pain in the head rather than the symptoms commonly associated with migraines. These headaches can last for a few hours up to a few days.

Hypoglycemia (defined as a fasting blood glucose below 70 mg/dL) has been reported to be associated with hypnic headaches as well, which are also referred to as alarm clock headaches. These types of headaches occur at roughly the same time every night and present with a mild to a severe throbbing pain in the head.

Diabetes

Low blood sugar is common for people with type 1 diabetes and can occur in people with type 2 diabetes who are taking insulin or certain medications. The average person with type 1 diabetes may experience up to two episodes of mild low blood sugar each week, and that's only counting episodes with symptoms. It can also be referred to as insulin shock or an insulin reaction.

Not Eating

Hypoglycemia can occur in people who are not eating regularly enough or are skipping meals entirely. When there is not enough food to turn into glucose, blood sugar levels drop.

Generally, not eating enough carbohydrates and eating foods with less carbohydrates than usual without reducing the amount of insulin taken can cause low blood sugar. Timing of insulin based on whether your carbs are from liquids or solids can affect blood sugar levels as well. Liquids are absorbed much faster than solids. The composition of the meal—how much fat, protein, and fiber are present—can also affect the absorption of carbohydrates.

Those who have eating disorders and are on a fasting diet are more susceptible to hypoglycemia.

Binge Drinking

Heavy alcohol consumption can interfere with blood glucose levels because of the effects it has on insulin. When a person binge drinks, the body's process of releasing insulin becomes inhibited. Since insulin is used to help regulate blood sugar, this hindrance can cause an imbalance in blood sugar levels.

Alcohol has also been shown to inhibit the body's process of creating sugars from its own fat or protein stores, decrease growth hormone levels, and cause hypoglycemia without the typical symptoms.

Reaction to Medications

Hypoglycemia can also occur in reaction to certain medications. In those with diabetes, the medications they take to help manage their condition can sometimes cause low blood sugar. People who do not have diabetes but are taking a diabetes medication may also develop hypoglycemia.

Diabetes medications that can lead to low blood sugar include:

• Insulin
• Metformin, if used with sulfonylureas
• Thiazolidinediones, if used with sulfonylureas
• SGLT2 inhibitors

Other types of medications that can in rare cases lead to low blood sugar include:

• Beta-blockers
• Cibenzoline and quinidine
• Indomethacin
• Pentamidine or gatifloxacin

Tumors

Rare tumors known as insulinomas can form in the pancreas and lead to the overproduction of insulin. Since insulin helps keep blood sugar levels regulated, having too much of it can lead to a drop in glucose levels and result in hypoglycemia.

Hormone Deficiencies

Hormones play a vital role in glucose levels within the body, specifically cortisol. This hormone helps in many regulatory processes when it comes to glucose levels, such as insulin signaling, the breaking down of fats to release fatty acids, and glucose utilization.

When cortisol levels are imbalanced, they cannot help with these processes. Research has shown that those with Addison’s disease (where the body doesn't produce any of the hormones cortisol and aldosterone) are at a higher risk of hypoglycemia because it affects cortisol levels.

Reactive Hypoglycemia

Reactive hypoglycemia is when low blood sugar occurs between two to five hours after eating a meal. It is caused by an overproduction of insulin. The type of headache that occurs with reactive hypoglycemia is the same as those that occur in a typical case of hypoglycemia and affects both sides of the head near the temples. The pain is typically dull and throbbing.

Hyperglycemia

Headaches that occur with hyperglycemia (a fasting blood sugar of 125 mg/dL) tend to appear early and could be a sign that the blood sugar levels are higher than normal. Unlike hypoglycemia, hyperglycemia causes the blood vessels in the brain to constrict, resulting in headaches. They tend to be mild at first, but as the blood sugar levels continue to rise or are maintained at high levels, the headache may worsen.

Sugar Rush

Eating too much sugar can result in what is referred to as a sugar crash or sugar hangover. This occurs when too much sugar is eaten all at once. When the body consumes too much sugar or carbohydrates in one sitting, the pancreas goes into high gear to create insulin to help break down the sugar and regulate blood glucose levels. When this happens, the sudden decrease in blood sugar causes hypoglycemia.

This can lead to several symptoms, such as an upset stomach and nausea, shakiness, tiredness, lightheadedness, mood swings, and headache. The type of headache associated with a sugar crash is similar to a typical hypoglycemic headache. The headache will likely be dull and throbbing in the temple area of the head.

Sugar Withdrawal

Sugar has the ability to affect specific neurotransmitters in the brain such as dopamine. Dopamine plays a role in mood, learning, memory, and behavior. It is also an important reward pathway found in the brain, and thus, plays a vital role in feelings of satisfaction and pleasure.

When a person consumes too much sugar on a regular basis, the levels of dopamine become disrupted. Sugar is considered to be an addictive substance because of how it affects these levels. The more sugar a person consumes on a regular basis, the more sugar will be needed for that reward center to activate.  

This is why when someone decides to limit their sugar intake after a prolonged period of consuming high amounts, they would suffer from withdrawal, much like they would if they were to quit smoking or using drugs. If the reduction in sugar is drastic, it can lead to a migraine-type headache. This occurs on the first day of a new sugar-free diet and tends to lessen over the first few days or weeks as the brain adjusts to life without sugar.

A Word From Verywell

Sugar is needed in the body for it to function normally, but consuming too much or too little sugar can wreak havoc on many systems. In the short term, eating sugar in excess may seem like a good idea, but that’s only because of how it affects the reward center of the brain. The truth is excess sugar upsets the entire balance of the body and that is why it can lead to unwanted effects such as headaches or migraines. On the flip side, cutting out sugar entirely seems like a healthy choice to make, but too little sugar in the body causes problems as well. To avoid these complications, avoid added sugars wherever possible, and remember that moderation is key when it comes to sugar consumption.