Yes, the keto diet can cause hypoglycemia, especially in the first few weeks. When you drastically cut carbohydrates, your body’s primary fuel source disappears, and blood sugar levels can drop below the normal range. This is a known and documented effect of the diet, though it is not a universal experience for everyone who tries it.
What Is Hypoglycemia and How Is It Defined?
Hypoglycemia is the medical term for low blood sugar. It is generally defined as a blood glucose level below 70 mg/dL. For most healthy adults, the normal fasting blood sugar range is between 70 and 99 mg/dL.
Symptoms usually appear when blood sugar drops below this threshold. Common signs include shakiness, sweating, confusion, irritability, rapid heartbeat, and hunger. In more severe cases, blood sugar can drop low enough to cause seizures or loss of consciousness, though this is rare outside of people taking diabetes medications.
For people on the keto diet, the drop is usually mild and temporary. But it can still produce uncomfortable symptoms that disrupt daily life.
Why Does the Keto Diet Cause Blood Sugar to Drop?
Carbohydrates are the body’s preferred and fastest source of glucose. When you eat carbs, your digestive system breaks them down into glucose, which enters the bloodstream and raises blood sugar. The keto diet restricts carbohydrates to roughly 20 to 50 grams per day, which is far below the typical American intake of 200 to 300 grams.
With almost no dietary glucose coming in, blood sugar levels naturally fall. The body responds by releasing stored glucose from the liver, but those stores are limited. Once liver glycogen runs low, the body shifts to burning fat for fuel, producing ketones as a byproduct. This metabolic state is called ketosis.
The transition period is when hypoglycemia is most likely. The body is still adjusting its glucose production and insulin signaling. Some people adapt quickly, while others take weeks to stabilize.
Who Is Most at Risk for Keto-Induced Hypoglycemia?
Certain groups are more vulnerable to low blood sugar on a keto diet. People taking diabetes medications, particularly insulin or sulfonylureas, face the highest risk. These drugs actively lower blood sugar, and when combined with severe carb restriction, the risk of dangerous hypoglycemia increases significantly.
Anyone on diabetes medication should not start a keto diet without medical supervision. Doses often need to be adjusted before starting, and blood sugar monitoring is essential.
Other groups at higher risk include older adults, people with kidney or liver disease, and those who exercise heavily. Alcohol consumption can also worsen hypoglycemia because the liver prioritizes clearing alcohol over producing glucose.
For healthy people without diabetes, keto-induced hypoglycemia is usually mild and self-correcting. But it can still cause symptoms that feel alarming.
Symptoms of Low Blood Sugar on Keto
The symptoms of hypoglycemia on keto are the same as hypoglycemia from any cause. They typically develop quickly and can include:
- Shakiness or tremors
- Sweating and clamminess
- Rapid heartbeat
- Confusion or difficulty concentrating
- Irritability or mood changes
- Dizziness or lightheadedness
- Intense hunger
These symptoms are caused by the body’s stress response to low glucose. The brain relies heavily on glucose for energy, and when levels drop, cognitive function suffers. This is why confusion and brain fog are common.
One important distinction: keto flu and hypoglycemia are not the same thing. Keto flu refers to a cluster of symptoms like fatigue, headache, and nausea that occur during the first week of carb restriction. Hypoglycemia is a specific blood sugar reading below 70 mg/dL. Both can occur simultaneously, but they are separate conditions.
Can Ketones Mask the Symptoms of Hypoglycemia?
This is a question researchers are still studying. Some evidence suggests that when the brain has ketones available as an alternative fuel, it may tolerate lower blood sugar levels without producing symptoms. This concept is sometimes called “relative hypoglycemia” or “asymptomatic hypoglycemia.”
In practical terms, a person in deep ketosis might have a blood sugar reading of 60 mg/dL but feel completely normal. The brain is running on ketones, so the glucose deficit does not trigger the usual alarm system.
This is not necessarily dangerous for healthy people, but it creates a problem: you cannot rely on symptoms alone to tell you if your blood sugar is low. If you are checking blood sugar on keto and get a low reading without symptoms, that is generally not an emergency. But if you have symptoms, treat them regardless of what the meter says.
How to Treat Hypoglycemia While on Keto
If you experience symptoms of low blood sugar on keto, the standard treatment is to consume fast-acting carbohydrates. This temporarily breaks ketosis, but it is the correct and safe response. Do not ignore symptoms or try to “push through” them.
Fast-acting carbs include glucose tablets, fruit juice, regular soda, or honey. The general guidance for treating hypoglycemia is to consume about 15 grams of fast-acting carbohydrate, wait 15 minutes, and recheck blood sugar if you have a meter. Repeat if symptoms persist.
For people who want to stay in ketosis, some clinicians recommend consuming a small amount of carbohydrate and then resuming the diet once blood sugar normalizes. A single episode of carb intake will temporarily raise insulin and halt ketone production, but ketosis typically resumes within a day or two.
If you do not have diabetes and are not on blood sugar-lowering medication, you likely do not need to check blood sugar routinely on keto. But if you experience recurrent symptoms, a home glucose meter can help you understand what is happening.
How Long Does Keto Hypoglycemia Last?
For most people, the low blood sugar phase is temporary. It typically lasts for the first one to two weeks of the diet, during the transition from glucose burning to fat burning. As the body becomes fat-adapted, the liver ramps up glucose production through a process called gluconeogenesis, which produces glucose from protein and other precursors.
Once this adaptation is complete, blood sugar levels usually stabilize in the low-normal range. Many people on established keto report fasting blood sugar readings in the 70s or 80s, which is normal and healthy.
If low blood sugar symptoms persist beyond the first few weeks, that is a reason to check in with a doctor. It may indicate that the diet is not working well for your body, or that an underlying condition is being unmasked.
How to Prevent Hypoglycemia on Keto
Prevention starts with understanding your risk. If you have diabetes or take any medication that lowers blood sugar, talk to your doctor before starting keto. Medication adjustments may be needed.
For everyone else, a few practical strategies can reduce the chance of low blood sugar:
- Transition gradually rather than cutting carbs all at once
- Stay hydrated and maintain adequate salt intake
- Do not skip meals, especially in the first two weeks
- Include protein at every meal to support gluconeogenesis
- Limit alcohol, especially on an empty stomach
Some people find that eating smaller, more frequent meals helps during the transition. Others do better with three larger meals. There is no single right approach, and individual response varies.
When to See a Doctor
You should see a doctor before starting keto if you have diabetes, take any medication that affects blood sugar, have liver or kidney disease, or have a history of disordered eating. These conditions change the risk calculation significantly.
You should also see a doctor if you experience severe symptoms of hypoglycemia, such as confusion, fainting, or seizures. These are medical emergencies and require immediate attention.
Recurrent low blood sugar symptoms that do not resolve after the adaptation period also warrant a medical evaluation. Persistent hypoglycemia can be a sign of an underlying metabolic issue that has nothing to do with your diet.
Is Keto-Induced Hypoglycemia Dangerous?
For healthy people without diabetes, keto-induced hypoglycemia is usually mild and temporary. It is uncomfortable but not typically dangerous. The body has multiple systems in place to prevent blood sugar from falling to life-threatening levels, including the release of counter-regulatory hormones like glucagon and epinephrine.
For people on insulin or sulfonylureas, the risk is genuinely serious. These medications can drive blood sugar dangerously low, and when combined with severe carb restriction, the result can be severe hypoglycemia requiring emergency treatment. This is why medical supervision is non-negotiable for this group.
The honest position is that keto-induced hypoglycemia is a real phenomenon, but its severity depends almost entirely on who you are. A healthy person may feel shaky for a week. A person on insulin may end up in the emergency room. Know which category you fall into before starting.
Frequently Asked Questions
Can the keto diet cause low blood sugar in people without diabetes?
Yes, it can, especially in the first two weeks of the diet. The drop is usually mild and temporary, and symptoms typically resolve once the body adapts to burning fat for fuel.
What should I eat to raise blood sugar quickly on keto?
Fast-acting carbohydrates like glucose tablets, fruit juice, or regular soda are the standard treatment for hypoglycemia. This will temporarily pause ketosis, but it is the safe and correct response to low blood sugar symptoms.
Is it dangerous to have low blood sugar on keto?
For healthy people, it is usually not dangerous and often resolves on its own. For people taking insulin or other diabetes medications, it can be genuinely dangerous and requires medical supervision.
Can I stay in ketosis and still treat hypoglycemia?
You cannot treat hypoglycemia without carbohydrates, so you will temporarily exit ketosis. Once your blood sugar normalizes, you can resume the keto diet and ketosis typically returns within a day or two.
