What is keto flu? 6 keto flu symptoms and their remedies

From the desk of
Luis Villaseñor
ScienceWhat is keto flu? 6 keto flu symptoms and their remedies

If you feel lousy on a keto diet, it’s hard to feel like what you’re doing is worth it. Whether your goal is to lose some fat, gain muscle or just become healthier, suffering through headaches, muscle cramps, constipation, insomnia, and other keto flu symptoms can ruin the desire to keep going.

It doesn’t have to be this way. Sure, any worthwhile dietary change comes with obstacles. But if you get the “keto flu” (not everyone does!) and it persists beyond a few days, then it’s time to reexamine your approach to the keto diet.

Are you hydrating properly? Getting enough electrolytes? Eating a nutrient-dense, fiber-rich diet? Are your macros dialed in? Problems in any of these areas can cause keto flu symptoms. And the remedies are generally straightforward.

Also, keep in mind that your symptoms aren’t necessarily tied to your keto diet. Just because they’re present on keto doesn’t mean that keto is the cause.

Take headaches, for example. According to one review paper, the top risk factors in people with chronic headaches are mood disorders, medication usage, stress, and poor sleep. Some of these factors tie indirectly to keto, but they’re nonetheless outside the diet bucket. Correlation doesn’t prove causation.

In this article, I’ll be providing practical tips to handle the six most common keto flu symptoms. First, though, let’s cover why keto flu happens.

What Is Keto Flu?

Keto flu is not really a type of flu. More so, it’s a catch-all term for the constellation of symptoms associated with a ketogenic diet. These symptoms include:

  • Headache
  • Weakness and fatigue
  • Low energy
  • Insomnia
  • Irritability
  • Diarrhea
  • Constipation
  • Muscle cramps

Depending on the person, mild symptoms are normal when transitioning to keto—especially when transitioning from a high-carb diet. Some explanation will help.

When you reduce your carbohydrate intake, such as when going to a paleo, keto, or carnivore diet, your brain won’t be able to anticipate the resultant drop in its traditional fuel source: blood glucose. This drop in blood glucose can cause headaches, low energy, and sometimes cravings.

This situation shouldn’t last long. Within a few days, the body starts producing ketones to switch the brain’s primary energy source from glucose to ketones. If keto flu symptoms persist, I then begin to look elsewhere—and I look first to electrolytes, specifically sodium.

In my coaching career I’ve worked with thousands of clients. Among them, low sodium is the leading cause of chronic keto flu symptoms. It makes sense. Keto diets increase urinary sodium loss. Plus, if you’re eating fairly clean whole foods, those diets typically aren’t very salty to begin with. The bulk of the average American’s dietary sodium comes from processed foods.

After electrolytes, I look at other micronutrients, fiber, hydration habits, and correct macro partitioning. All of these areas are important to a healthy lifestyle, and I’ll review them in the keto flu remedies section.

But before we cover remedies, let’s do a deeper dive into the symptoms of keto flu.

6 Symptoms of Keto Flu

If you want to fix frustrating keto flu symptoms, it helps to first understand them. Here are the 6 most common ones I see:

#1: Headaches

Dehydration, inadequate sodium, stress, sleep deprivation, drugs, hangovers, brain inflammation, low blood sugar—the list of potential headache causes is long. Because of this, troubleshooting yours could take some detective work.

Some of these causes may be related to keto. For instance, low blood sugar for the first few days of carb restriction can cause headaches. Headaches are also a hallmark symptom of sodium deficiency.

But sometimes, a ketogenic diet can help with headaches. In one study, a keto diet improved migraine symptoms in 90% of patients, while a standard low-calorie diet had no effect.

For more on this topic, read the blog: What causes keto headaches? (And what to do about them).

#2: Fatigue or weakness

I hear this complaint from many keto dieters. They feel sluggish, low energy, weak, and fatigued after cutting out carbs.

This problem often manifests during exercise. You just can’t kill it in the gym anymore. Or you get super winded from a regular cardio routine. What’s causing this?

It could be that your body isn’t fat-adapted yet. It takes time to transition to burning fat as an energy source, especially if you’re used to burning sugar.

It could also be an electrolyte issue. Electrolytes play crucial roles in cellular respiration, the process by which food energy is converted into usable energy (ATP).

Or it could be that you perform best with some carbs in your system. I’m not dogmatic about this: I understand that keto isn’t the optimal performance diet for everyone, everywhere.

For more on this topic, read the blog: Do electrolytes give you energy?

#3: Insomnia

Many sleepless nights can be traced back to caffeine. In a slow caffeine metabolizer, a late morning cup of coffee can impact restfulness at bedtime.

Medications, mood disorders, and poor sleep hygiene can also disrupt sleep. If you’re spending your evenings bathed in fluorescent light, that’s bad news for your melatonin (sleep hormone) levels.

What about insomnia on keto? Here are three potential causes:

  1. Transitioning from carbs (discussed earlier)
  2. Increased bathroom trips (keto has a diuretic effect)
  3. Inadequate sodium, potassium, or magnesium

For more on this topic, read the blog: Keto insomnia: causes and remedies.

#4: Mood issues

Irritability follows from the other keto flu symptoms. If you aren’t feeling well, you’re bound to be cranky. This can be exacerbated by the transition from carbs to fat. Low blood sugar can make you feel “hangry”.

This will be short-lived though, and this crankiness is likely just a sign that you are currently metabolically inflexible. But assuming you’re cutting net carbs low enough, you’re transitioning to becoming more efficient at using fat and ketones as fuel. So, all in all, it’s kind-of a good sign.

Then there are electrolytes. In rats, sodium deprivation causes sluggish listlessness. And in humans, magnesium deficiency has been linked to both anxiety and depression.

For more on this topic, read the blog: Electrolytes and your mood: A surprising link.

#5: Muscle cramps

In the throes of a muscle cramp, it’s hard to concentrate on anything else. They’re excruciating.

Scientists are still quibbling over what causes muscle cramps, but they appear to be driven by two main factors:

  1. Neuromuscular fatigue
  2. Electrolyte imbalances

On keto, we’re more worried about number two. And while potassium, magnesium, and calcium deficiencies can all cause cramping, I believe low sodium is the biggest offender.

For instance, football players who cramp more frequently ALSO have higher concentrations of sodium in their sweat. Recall that you’re also losing more sodium (through urine) on keto.

For more on this topic, read the blog: What causes muscle cramps? (And what to do about them).

#6: Diarrhea or constipation

In many ways, gut health is synonymous with general health. If your digestion doesn’t run smoothly, nothing will run smoothly.

Constipation and (less commonly) diarrhea can both occur when shifting off carbs. Eliminating carbs can:

  • Reduce fiber intake, affecting bowel regularity
  • Change the constitution of your gut microbiome
  • Cause issues for people with problems digesting fat

Most of the time, keto constipation or diarrhea are short-lived. If they aren’t, consider working with a functional (or integrative) medicine practitioner to heal your gut.

On another interesting note; whole food, low carb diets are also known to be “low waste” diets; meaning that you absorb most of what you eat, wasting little. I often joke: “less crap in, less crap out”: so it’s likely you will experience less bowel movements.

For more on this topic, read the blog: Keto diet constipation and diarrhea: Causes and remedies.

6 Remedies for Keto Flu

Time to get practical. You might have noticed a trend in the causes of keto flu symptoms thus far. There’s often a lot of overlap among them.

For that reason, many of the following remedies apply to keto flu symptoms generally. Still, some (like getting enough fiber) are specific to gut symptoms.

#1: Allow transition time

If you’re used to a high-carb diet, you may experience headaches or low energy / lethargy as you transition to keto. These should dissipate in a few days. Adapting to exercise on keto may take longer, but no more than a few weeks.

If you are used to training, remember that normally the body uses muscle glycogen (along with fatty acids) to fuel your workouts. Once you go low carb, it takes some weeks for your body to adapt to using more fatty acids. Glycogen use will be spared, but also refill by itself at an increased rate.

#2: Eat a micronutrient-dense diet

Micronutrient deficiencies can cause a host of symptoms. Prevent them by eating meat, fish, non-starchy vegetables, and other low-carb whole foods.

#3: Get enough electrolytes

The most important class of micronutrients for preventing keto flu symptoms? Electrolytes. Aim for the following daily intakes:

  • 4–6 grams of sodium (add between 1 – 5 grams more on sweaty days)
  • 3.5–5 grams of potassium (shoot for the upper end if possible)
  • 400–600 mg of magnesium (shoot for the upper end if possible)
  • 1 gram of calcium (you can get this from cheese and almond milk)

If you aren’t getting enough electrolytes through diet, you’ll need to supplement. One tasty way to make up for electrolyte deficiencies is with LMNT. Each stick pack contains a science-backed ratio of electrolytes—1000 mg of sodium, 200 mg of potassium, and 60 mg of magnesium—and 0 sugar, because we formulated LMNT with low-carb communities front-of-mind.

#4: Don’t forget fiber

Your keto plate should be filled with non-starchy vegetables like spinach, kale, asparagus, and broccoli. These powerhouses not only provide a boatload of vitamins and minerals, but they also contain lots of fiber to keep you regular.

#5: Hydrate properly

Dehydration could cause symptoms that are very similar to that of the keto flu. But for most people, if you’re drinking when thirsty, water intake isn’t going to be an issue. It’s usually a lack of electrolytes in your water.

Sip electrolyte water to thirst to prevent dehydration and electrolyte deficiency in one swoop.

#6: Get your macros right

Of all the macro mistakes on keto, the two most common are:

  1. Not getting enough protein
  2. Not sufficiently limiting carbohydrates

If you rush past your carb limit (about 30 grams net carbs for most people), you won’t be able to burn fat and keto-adapt. You could get stuck in an uncanny valley where the adaptation never happens and the malaise never ends.

You also need to get enough protein to support hormonal health, body composition, neurotransmitters, and more. Protein provides the building blocks of life (amino acids) and you can’t skimp on them.

Get your macros handled (along with the other remedies) and you’ll be well-positioned to banish your keto flu symptoms. I wish you the best of health!

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