UPDATED by FRANZISKA SPRITZLER, RD, CDCES
If you recently started a keto diet and are getting headaches, brain fog, or mental fatigue, don’t be surprised or overly concerned. You’re likely experiencing some of the common side effects that come with transitioning from a carbohydrate-based diet to a fat-based diet. The good news is that these symptoms for new keto eaters are temporary. Also, there are things you can do to help them go away or to be less bothersome while your body settles into the ketogenic lifestyle.
What Can Cause Headaches on a Keto Diet?
When transitioning from a typical high-carbohydrate diet to a low-carbohydrate, moderate-protein, higher-fat diet, your body needs time to adapt. When your body no longer has access to adequate carbs for fuel, it begins shifting to fat as its primary fuel source. This adjustment period usually lasts one to two weeks and can come with common, temporary side effects as your metabolism adapts to carb reduction. This adjustment period can feel similar to detoxing from alcohol or nicotine. Because of this, during the first week, it’s normal to experience a variety of detox-like or flu-like symptoms, commonly called the keto flu. One of the symptoms is headaches, which makes sense if you understand the transition process.
Lower Blood Glucose
Your brain is used to being powered by glucose rather than ketones. When you begin a keto diet, your body continues reaching for glucose, even when it’s no longer available and is instead creating ample ketones for energy. This may cause your blood glucose levels to decrease, especially if you are intermittent fasting. In this case, hypoglycemia is not cause for alarm. It’s part of the transition. Once your brain starts utilizing ketones rather than glucose for its main fuel, you should find some relief from your headache and begin to experience better energy levels and the known health benefits of staying in nutritional ketosis.
Dehydration
Rapid weight loss in the first week of keto is extremely common. However, a portion of this loss is water. When you’re in the transition stage of keto and using up your glycogen (stored glucose), your body excretes extra water. This is because every gram of glycogen is stored and released with at least three grams of water. So, as your body depletes its glucose reserves, it also eliminates significant amounts of water (and the bloating that goes along with it). If you don’t replenish that water by drinking frequently, you’ll get dehydrated and perhaps get the headache that often accompanies it.
Electrolyte Imbalance
When you significantly reduce your carbohydrate intake, your body naturally produces less insulin. That’s because insulin’s primary role is to help manage the glucose that comes from carbs. With less glucose coming in, less insulin is needed. As insulin levels drop, your kidneys begin to excrete more sodium, an essential electrolyte that helps regulate fluid balance and hydration. This sodium excretion can throw off the balance of other essential electrolytes too, such as potassium and magnesium. This imbalance is one of the main reasons people suffer from keto flu symptoms. If you find yourself getting a headache while on keto, it may be related to sodium loss.
Hormonal Changes
There’s a lot of misinformation and anecdotal information about the topic of hormones and ketones, yet what is abundantly clear in the literature is that any diet that results in rapid weight loss and a deliberate or natural reduction in calorie intake, will change diurnal rhythm (daily patterns) and signal hormonal changes that could potentially trigger headaches. Additionally, drops in insulin levels can directly lower estrogen levels and contribute to menstrual migraines.
How to Stop or Prevent Keto-Related Headaches
What can you do to help with a keto-related headache? Here are some easy remedies to try. They’re also good ongoing practices for your continued success on a ketogenic lifestyle, headaches or not.
- Hydrate
Avoid dehydration. Drink at least half of your body weight in ounces of water throughout the day. For example, if you weigh 150 pounds, you will want to drink 75 ounces (2.1 liters) of water daily. On top of this amount, if you consume coffee or other caffeinated drinks or diuretics, increase your water intake by about one cup of water per cup of coffee. Some people feel better when they supplement with electrolytes or drink bone broth or bouillon during this time. But this may not be required, especially if you heed the next three recommendations. - Salt Your Water
One easy way to make up for sodium lost on a keto diet is to add a pinch of Himalayan salt to each glass of drinking water. You can also add mineral drops to your water to boost your electrolytes. - Eat Enough Fat
When you’re used to eating a high-carb, low-fat diet, it may seem counterintuitive to suddenly be eating so much fat. But it’s essential to eat enough fat to ensure a successful keto transition and continue this way of eating as a lifestyle long term. It may also help relieve a headache and manage hunger. - Eat High-Quality, Nutrient-Dense Foods
To support your body during fat loss, it’s important to focus on nourishment and balance. Make sure you’re eating enough fat and protein to meet your needs, and avoid cutting calories too drastically. Losing fat too quickly can be stressful for the body and difficult to sustain. When planning meals, aim for whole, minimally processed foods whenever possible. Choosing options that are free from added hormones and pesticides can be a helpful way to support overall health while keeping your diet nutrient-dense and clean.
The Final Word
Hopefully, we’ve helped clear up your questions and perhaps your headache. But the main takeaway is that keto headaches are common during the transition to a high-fat, low-carb diet. They’re also temporary and will subside when your body adjusts to using ketones for fuel. In the meantime, follow our tips to stop or prevent headaches above.
Disclaimer: When starting a new diet, it’s always a good idea to get medical advice first, especially if you already have health risks or preexisting conditions. So always ask your health care provider or dietitian before making any major dietary change, including switching to a high-fat diet.
