The Keto Flu: Symptoms and How to Get Rid of It

Starting a ketogenic diet can feel a little like moving into a new house: exciting, full of potential… and then you realize you don’t know where the light switches are.
For many people, that “where are the switches?!” phase shows up as the keto flua short-term wave of unpleasant symptoms that can pop up when you cut carbs way down and your body starts shifting fuel sources.

The good news: it’s usually temporary. The better news: you can often make it a lot less dramatic with a few practical fixes.
The important news: “keto flu” isn’t an official medical diagnosis, and some symptoms can overlap with dehydration, illness, or (in people with diabetes) serious problemsso knowing what’s normal and what’s not matters.

Quick note: This article is for general education, not medical advice. If you have a medical condition, take prescription meds (especially for diabetes or blood pressure), are pregnant/breastfeeding, or you’re a teen still growing, talk with a clinician before attempting keto.

What Is the Keto Flu (and Why Does It Happen)?

The keto flu is a nickname for a cluster of symptoms some people experience during the first days (and sometimes weeks) of a very low-carb diet.
It’s basically your body saying, “Hey… where did my usual fuel go?” as it transitions from relying heavily on glucose (from carbohydrates) to using more fat and producing ketones.

Three main reasons you may feel lousy at first

• Water and electrolyte loss: When you reduce carbs, your body uses up stored glycogen (carbohydrate stored in muscles and liver). Glycogen is stored with water, so as glycogen drops, you lose water. Along with that water, you may lose more sodium and other electrolytes. This combo can trigger headaches, fatigue, dizziness, and muscle cramps.
• Fuel switching (“metabolic remodeling”): Your cells and enzymes need time to get efficient at burning fat and ketones. During that learning curve, your energy can diplike a phone in low power mode.
• Diet changes that affect digestion and sleep: A sudden shift in fiber intake, meal timing, caffeine habits, and fat quantity can cause constipation, diarrhea, nausea, or insomniaespecially if your menu goes from “sandwich life” to “cheese sticks and vibes.”

Keto Flu Symptoms: What People Commonly Report

Keto flu symptoms vary a lot. Some people feel mildly “off,” while others feel like they got hit with a pillow filled with bricks.
Common symptoms include:

• Headache
• Fatigue and low energy
• Brain fog (trouble focusing)
• Irritability or moodiness
• Dizziness or lightheadedness
• Nausea or stomach upset
• Constipation (sometimes diarrhea)
• Muscle cramps or weakness
• Trouble sleeping
• Cravings for carbs/sugar
• Bad breath (“keto breath”) as ketones rise

How to tell keto flu from “something else”

Keto flu is usually tied to a recent, significant carb reduction and tends to improve as your body adapts.
If you have a fever, severe sore throat, persistent vomiting, chest pain, fainting, confusion, trouble breathing, or symptoms that keep getting worsetreat it like a medical issue, not a diet rite-of-passage.

How Long Does the Keto Flu Last?

Many people notice symptoms within the first 1–3 days after dropping carbs, with the roughest stretch often happening in the first week.
For lots of folks, symptoms ease within a few days to about two weeks. Some people feel on-and-off symptoms longeroften because hydration/electrolytes aren’t dialed in, calories are too low, sleep is poor, or workouts are too intense too soon.

Translation: if you’re on day 4 and wondering if you permanently broke your bodyno. You’re probably just under-salted.

How to Get Rid of the Keto Flu (Or Make It Way Less Annoying)

Most keto flu remedies are surprisingly unglamorous: fluids, electrolytes, food quality, and a little patience.
Here’s what tends to help the most.

1) Hydrate, but don’t forget electrolytes

Drinking water is essential, but water alone can sometimes make you feel worse if you’re already low on sodium.
If you’re experiencing headaches, dizziness, or cramps, consider pairing fluids with electrolytes.

• Sodium: Salt your food. Sip broth. Choose electrolyte drinks with sodium (watch added sugar if you’re staying strict).
• Potassium: Keto-friendly sources include avocado, spinach, mushrooms, salmon, and plain Greek yogurt (if it fits your plan).
• Magnesium: Found in pumpkin seeds, almonds, spinach, and some supplements. Magnesium is often discussed for muscle cramps and sleep.

Safety note: If you have kidney disease, heart failure, uncontrolled high blood pressure, or take meds that affect electrolytes (like diuretics), talk to a clinician before supplementing sodium/potassium.

2) Don’t accidentally “crash diet” your calories

Keto flu is more likely to feel brutal if you go low-carb and low-calorie overnight.
If you’re under-eating, your body stacks stressors: less glucose + fewer calories + electrolyte loss = you feeling like a sleepy raccoon.

Make sure you’re eating enough overall, with adequate protein and keto-appropriate fats. If your appetite disappears at first, choose smaller, more frequent meals that are easy to tolerate.

3) Ease into keto instead of “carb cliff-diving”

Some people do better tapering carbs over 1–2 weeks rather than dropping to very low carb overnight.
A gradual approach can reduce the intensity of carb withdrawal-style symptoms and give your body time to adjust.

Example taper (not a rule, just a concept): reduce sugary drinks and desserts first, then refined grains, then starchy sideswhile increasing non-starchy vegetables and protein.

4) Fix constipation before it becomes your personality

Constipation is common early on, especially if fiber drops.
To help:

• Increase fiber gently: Non-starchy vegetables (broccoli, zucchini, leafy greens), chia/flax, and small portions of berries if allowed.
• Include fluids + sodium: Dehydration makes constipation worse.
• Move daily: Walking helps gut motility without wrecking you like a bootcamp class.
• Consider magnesium (with clinician guidance if you have medical conditions or take medications).

5) If nausea hits, adjust fat quality and timing

A sudden jump in fat can upset your stomachespecially if it’s mostly heavy cream, fried foods, and “keto desserts” made of pure optimism.

• Choose easier fats: olive oil, avocado, nuts, nut butters, salmon.
• Try smaller meals until your digestion adapts.
• Keep meals simple: protein + cooked veggies + added fat, rather than a complicated “keto casserole tower.”

6) Scale back intense workouts for a week

High-intensity exercise can feel harder during the transition because your body isn’t fully efficient at using fat/ketones yet,
and your glycogen stores may be lower.

For the first week, prioritize:

• Walking, light cycling, easy strength sessions
• Extra hydration and electrolytes around workouts
• More sleep (seriouslysleep is a performance enhancer that doesn’t cost $79.99/month)

7) Sleep like it’s your job

Sleep disturbances can happen early, and lack of sleep makes everything worse: cravings, irritability, headaches, and hunger signals.
Try:

• Consistent bedtime/wake time
• Lower caffeine after late morning
• A protein-forward dinner with non-starchy vegetables
• Magnesium-rich foods in the evening (if tolerated)

8) Consider whether you actually need strict keto

Not everyone needs deep ketosis to meet their goals. Some people do better with a less restrictive lower-carb approach
that still emphasizes whole foods and balanced mealswithout the “why do I taste pennies?” phase.

Who Should Be Extra Careful (or Avoid Keto Without Medical Supervision)?

Keto can be medically appropriate in specific situations (for example, certain epilepsy protocols under clinical care), but it’s also a restrictive diet.
It may not be a good ideaespecially without professional guidanceif you are:

• A teenager (growth and nutrient needs are high; restrictive diets can backfire)
• Pregnant or breastfeeding
• Living with diabetes or taking glucose-lowering medications
• Managing kidney disease, liver disease, pancreatitis, or gallbladder problems
• With a history of eating disorders or disordered eating patterns

Keto flu vs. diabetic ketoacidosis (DKA): not the same thing

Nutritional ketosis (from a keto diet) is different from diabetic ketoacidosis (DKA), a dangerous condition that can happen in people with diabetes
when insulin is too low and ketones rise to unsafe levels.

If you have diabetes and experience symptoms like vomiting, abdominal pain, rapid breathing, confusion, or fruity breath with feeling very unwell,
seek medical care promptlydon’t try to “salt it out.”

A Practical “Keto Flu Rescue Plan” (Simple Checklist)

If your keto flu symptoms are mild-to-moderate, try this 48-hour reset:

• Fluids: Aim for steady hydration through the day (not a water-chugging contest).
• Sodium: Add broth or salt meals appropriately.
• Food: Eat enough calories; include protein, cooked vegetables, and easier-to-digest fats.
• Fiber: Add non-starchy veggies; consider chia/flax in small amounts.
• Movement: Walk 20–40 minutes daily; pause intense workouts.
• Sleep: Prioritize an early bedtime and consistent wake time.

If symptoms are not improving after about 1–2 weeks, or they’re severe at any point, get medical guidance.
Sometimes the “fix” is simply that keto isn’t a fit for your body, lifestyle, or health needs.

FAQs People Ask When They’re Staring at Their Salt Shaker

Is the keto flu a sign ketosis is “working”?

Not necessarily. Some people enter ketosis with minimal symptoms; others feel rough even if they’re not in deep ketosis yet.
Keto flu mostly reflects the transition and how your body is handling fluid balance, electrolytes, and dietary change.

Can I prevent keto flu completely?

You can’t guarantee it, but you can reduce the odds by tapering carbs, staying hydrated, getting adequate sodium, and avoiding an extreme calorie cut.

What’s the fastest way to feel better?

For many people, the quickest relief comes from addressing electrolytes (especially sodium) and hydration,
then ensuring they’re eating enough and sleeping well.

Do I need electrolyte supplements?

Not always. Many people can manage with food and beverages (broth, salted meals, potassium-rich keto foods).
Supplements can be helpful for some, but they’re not risk-freeespecially if you have kidney/heart issues or take certain medications.

Conclusion: The Keto Flu Is Annoying, Not Magical

Keto flu symptomsheadache, fatigue, brain fog, cramps, nausea, constipation, and irritabilityoften show up early when carbs drop and your body shifts gears.
Most of the time, it’s temporary and manageable.
The best “get rid of it” strategy is simple: hydrate + replace electrolytes + eat enough + sleep + ease your workouts.

And if you’re a teen, have diabetes, or have any chronic medical condition, treat keto like a serious interventionnot a casual weekend experiment.
Your body isn’t a smartphone; you can’t just “restart” and hope for the best.

Experiences People Commonly Have With Keto Flu (and What Helps)

Let’s talk about what the keto flu often looks like in real lifebecause advice is great, but it’s even better when you can picture how it plays out.
The examples below are typical scenarios drawn from common patterns people report when transitioning to very low carb eating.
Think of this as a “you are here” map, not a prophecy.

Experience #1: “Day 2 headache” that feels suspiciously personal

A lot of people describe a headache that arrives 24–72 hours after cutting carbs. It’s often paired with feeling a little lightheaded when standing up,
plus a general “my brain is buffering” vibe. In many cases, the missing piece is sodium and fluids.

What often helps quickly is salting meals more intentionally and adding a salty fluid like brothespecially if you’ve also been drinking lots of plain water.
People are sometimes surprised that the fix isn’t exotic (no rare jungle berry needed), just basic fluid balance.
If the headache improves within hours of electrolytes and hydration, that’s a big clue you were simply under-replaced.

Experience #2: “I’m doing keto” accidentally turns into “I’m not eating”

Another common story: someone cuts carbs, appetite drops, and they end up unintentionally eating far fewer calories than usual.
That can make fatigue and irritability hit harder. Then workouts feel awful, sleep gets weird, and cravings show up like an uninvited houseguest who brought a megaphone.

In practice, many people feel better when they add back enough total foodespecially protein and vegetablesrather than trying to white-knuckle through the transition.
A helpful approach is choosing easy meals for a few days: eggs plus sautéed greens, chicken with olive-oil dressed salad, salmon with zucchini, or Greek yogurt with a few berries (if it fits).
The goal is not “perfect keto,” it’s “stable human energy.”

Experience #3: Muscle cramps at night (a.k.a. your calves file a complaint)

Night cramps or “charley horses” are frequently mentioned during the first week. This often overlaps with increased urination, sweating workouts,
or simply not getting enough electrolytes. Some people find relief by improving overall electrolyte intake:
sodium at meals, potassium-rich keto foods (like avocado and spinach), and magnesium-rich foods in the evening.

The experience tends to improve when people stop treating electrolytes like an optional accessory and start treating them like a basic requirementlike shoes in public.
If cramps persist, it’s also worth looking at training load (too intense too soon), hydration patterns, and whether constipation or low fiber is creating extra stress in the system.

Experience #4: Digestive dramaconstipation for some, diarrhea for others

Keto flu “gut symptoms” are common, especially if the diet change is abrupt. Constipation can happen when fiber drops and water loss increases.
Diarrhea can happen when fat intake rises suddenly or when sugar alcohols and “keto treats” enter the chat.

People often do better when they:

• Prioritize cooked non-starchy vegetables (easier on digestion than huge raw salads at first)
• Add fiber gradually (chia/flax, berries in small amounts if allowed)
• Pick fats that digest more easily (olive oil, avocado) rather than going all-in on heavy cream
• Reduce “keto snack products” for a week and focus on whole foods

Experience #5: The turning pointenergy comes back, cravings calm down

Many people who stick with keto long enough to adapt describe a turning point somewhere between the end of week one and week three:
less brain fog, steadier energy, and fewer intense cravings. That doesn’t mean keto is “best” for everyonebut it does suggest the transition phase is often the hardest part.

If someone never reaches that calmer phase, it’s commonly due to one of three things: (1) persistent low electrolytes/hydration,
(2) consistently under-eating, or (3) keto simply not being a good match for their body, lifestyle, or health situation.
In those cases, many people feel better switching to a less restrictive lower-carb approach rather than forcing deep ketosis.

Bottom line: the keto flu experience is usually a temporary adjustment, not a test of toughness.
If your symptoms are manageable and improving, you’re likely adapting. If they’re severe, worsening, or persistentespecially with a medical conditionget professional guidance.