Digestion · Keto · Weight Loss Nov 20, 2025

Keto Diet Side Effects: Risks, How to Manage & Prevent Them

While the ketogenic diet can offer powerful benefits like weight loss and improved blood sugar control, it’s not without potential drawbacks. Many people experience short-term side effects (“keto flu”), and there are also longer-term risks, such as nutrient deficiencies, kidney stones, or bone health issues. In this guide, we’ll break down the most common keto diet side effects, explain why they happen, and give you practical strategies to prevent or minimize them.

Keto Breath - Fact

Though it seems like a tall tale, this keto diet side effect is fact. While the body is going through a metabolic change with a new diet, shifting from using glucose to ketones as its main energy source may involve the casual case of “keto breath.” Here’s why: once in ketosis, one way your body disposes of ketones is by exhaling, which can cause a strange metallic taste in your mouth. This is known as “keto breath,” and besides causing your partner to avoid getting too close to you, it’s harmless.

Tips to combat keto breath:

Give it time. The body goes through many changes as it adjusts to a large lifestyle change, and the symptoms are most dramatic in the beginning!
Staying properly hydrated helps to flush out more toxins so you can cut keto breath in its tracks. Dry mouth is also a leading cause of bad breath.
Cut back on protein since it’s harder to digest and often requires more effort for the body to eliminate.
Add more celery, lemon, and parsley to your diet to improve your breath.

Keto Weight Loss - Fact

Weight loss is one of the most noticeable and sought-after side effects of the keto diet. When in ketosis, your stored body fat and the fat from your diet are burned as energy, helping you shed stubborn excess fat while controlling your appetite. This is one effect that most people agree is one of the biggest reasons to do the keto diet!

Learn more!

Keto Causes Ketoacidosis - Fiction

While ketoacidosis has the word “keto” in it, the two are completely unrelated.

Ketoacidosis is a life-threatening condition that occurs when the body has dangerously high levels of ketones and glucose in the blood. This is typically triggered by type 1 diabetes because the body doesn’t have enough insulin to move glucose from the blood into cells.

Nutritional ketosis, on the other hand, occurs when the body burns fat instead of carbs and glucose.

The Keto Flu - Fact

The keto flu is one of the more unpleasant side effects of the keto diet, but thankfully, is short-lived.

When in ketosis, your body swaps carbs and glucose for fat as its main source of fuel. This major metabolic change can be tough on the body and will often result in flu-like symptoms, known as the keto flu. While everyone experiences keto flu differently, some common symptoms include brain fog, insomnia, digestive issues, and nausea. Keto flu symptoms are most likely to occur in the first two weeks as your body transitions into ketosis, but once you’re through it, you’ll get to enjoy the positive effects of the keto diet!

Tips to combat the keto flu:

Drink Organic Bone Broth Protein daily to nourish your body with nutrients that can help restore balance and get you back to feeling your best
Intermittent fast for 13-16 hours to boost your ketone levels and help you advance into ketosis
For even more solutions, check out our article, The Ultimate Guide to the Keto Flu

Keto Crotch - Fiction

Some sources have claimed that keto dieters can experience “keto crotch,” suggesting that ketosis can cause a funky smell down there. We’re happy to share that there’s no evidence to support this, so you don’t have to worry about the keto diet affecting your sex life.

Ketones in Your Blood - Fact

If you’re in ketosis, you have a higher level of ketones in your blood, which is a really good thing! On the keto diet, ketones are your main fuel source, so ketones are your friend.

Here’s how to test if you’re in ketosis. After at least 2-3 days of eating keto, you can use either a ketone monitor, urine testing strips, or breath testing strips to confirm your current ketone levels. Many experts consider ketone levels anywhere between 0.3-5.0 mmol/L to be a sign of being in ketosis.

It is important to note, however, that high ketone levels are not the be-all, end-all of the keto diet. If you have relatively low ketone levels and are seeing results like weight loss, increased energy, and enhanced cognitive function, then you’ve likely found your keto sweet spot, and there’s no need to strive for higher blood ketone levels.

Keto Suppresses Appetite - Fact

This is one side effect that many on the keto diet love. It’s normal for keto dieters to go long periods without ever feeling hungry because keto keeps blood sugar levels stable, which, in turn, helps to control cravings. Ketones also suppress ghrelin (aka your hunger hormone) and increase your body’s levels of cholecystokinin (aka the hormone that tells your brain you’re full).

Keto Headache - Fact

Keto headaches typically occur when the body is first adapting to the sudden lack of carbohydrates and sugar. Hypoglycemia combined with electrolyte imbalances is also a common cause of headaches during the transition to keto.

Tips to combat the keto headache:

Eat mineral-rich foods like bone broth, a veggie bouillon, or pickle juice to help correct electrolyte imbalances
Drink warm water with salt or coffee with salt
Always, always, always stay hydrated

Keto Diarrhea - Fact

If your previous diet involved processed foods, sugary desserts, and alcohol, you may fall victim to keto diarrhea after the sudden diet change. If you’re experiencing keto diarrhea, it may simply be a symptom of the keto flu, or something more. If the problem persists, you may be making some keto diet mistakes that are taking their toll on your GI tract, your bile production, or your magnesium levels.

Tips to combat keto diarrhea:

Stop cooking with industrial oils like vegetable oil, canola oil, and peanut oil. These highly processed oils are rich in omega-6, which can upset the stomach.
Watch out for sugar alcohols like sorbitol and xylitol. They may be keto-friendly solutions that satisfy your sweet tooth, but they have laxative effects when consumed in too much.
Too much protein can cause digestive issues like diarrhea, so make sure to combine your fish and meat with a healthy side of fiber-rich veggies.
Stay hydrated! The importance of drinking enough water on the keto diet should not be underrated.

Keto Constipation - Fact

Unfortunately, a common keto diet side effect is constipation (we even dedicated an entire article to it). As we established earlier, cutting back on carbs quickly can cause serious stress on your body, especially your GI tract, and since many high-fiber foods (think whole-grain bread and raisin bran cereal) are no longer allowed on the keto diet, it can prevent things from running smoothly and regularly.

Tips to combat keto constipation:

Drink more water! Staying properly hydrated helps your body flush out waste
Eat keto-friendly, fiber-rich foods like berries and vegetables
Try 10-30 minutes of daily cardio to get your juices flowing

Increased Focus and Energy - Fact

Clear focus and a boost in energy are more side effects coveted by those on the keto diet.

Did you know that your brain is made up of 60% fat? This means eating fatty foods is exceptionally beneficial when it comes to nourishing your favorite fatty organ. There’s also an overwhelming amount of evidence suggesting that the brain can focus and retain more when it runs on ketones rather than glucose. This is because ketones provide more energy per unit oxygen used, increasing the overall efficiency of brain functions.

There’s also a reason why people report feeling more energized while on the keto diet. It turns out that being in ketosis also improves the body’s energy levels, thanks to the dramatic increase in mitochondria production in the body, the essential agents responsible for fueling your cells and organs with the energy needed to get their job done.

Conclusion

While the keto diet comes with some unpleasant side effects, the good news is that they’re mostly limited to the first two weeks as your body adjusts to the new metabolic changes. Afterward, you can enjoy the positive side effects of being in ketosis, like weight loss and a lack of energy crashes. Your endurance also improves, making exercise and physical activities much more sustainable.

Frequently Asked Questions (FAQ)

What is the “keto flu”?
It’s a group of temporary symptoms (fatigue, headache, nausea, dizziness) that many people experience when they first start keto, often due to electrolyte shifts.

How long do keto side effects last?
Keto flu typically resolves within a few days to a couple of weeks, especially if you stay hydrated and replenish electrolytes.

Why do people get constipated on keto?
A very low-carb diet often means lower fiber intake, which can lead to digestive issues and constipation.

Are there long-term risks to following the keto diet?
Yes — possible risks include nutrient deficiencies, kidney stones, reduced bone density, and increased cholesterol, especially without proper planning.

How can you reduce keto side effects?
To mitigate side effects: stay well-hydrated, use electrolytes (sodium, magnesium, potassium), eat fiber-rich low-carb veggies, and consider supplementing vitamins and minerals.

Is the keto diet safe long-term?
Long-term safety is still being studied. Some research shows risks like liver stress, kidney stones, and nutrient gaps, especially if the diet isn’t well-balanced.

UP NEXT: Getting Into Ketosis: 3 Easy Tips to Start Burning Fat Fast

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