Weight Loss

Is a Keto Diet Dangerous?

The keto diet is something that has boomed in popularity over recent years, claiming health and weight loss benefits. But what is it? And is a keto diet dangerous? 

We’ll find out in this tell-all, highly researched article. 

A keto diet is where you significantly reduce carbohydrates in your diet, whilst upping fat intake to enter a state called ketosis, where your body relies on stored fat cells for energy rather than carbohydrates (1).

This can lead to weight loss, as the body utilizes fat reserves within the body, in order to fuel activity. 

However, like many weight loss diets, there are some things to be aware of when asking yourself is a keto diet dangerous? 

What are the side effects of ketogenic diet – 6 things to be aware of


May put your kidneys under strain

A key focus of the ketogenic diet is around significantly reducing your carbohydrate intake, and increasing the amount of fat you consume. This kind of change can impact the processes going on internally. 

A sudden and significant increase of fats in your diet can lead to more acidic blood and urine, which puts your kidneys under additional strain as they work to filter the acidic elements out [2]. The same research has also found that it can increase your likelihood of developing kidney stones. 

As such, if you suffer with kidney stones or you have a condition where your kidneys may be impacted, it might be a good idea to speak to your doctor before you consider starting on a keto diet. Furthermore, those who have chronic kidney conditions should actively avoid it. 

May significantly lower your blood sugar levels

There are many queries around whether you should consider a ketogenic diet if you have diabetes. 

As you’re effectively removing almost all carbohydrates from your diet (less than 50g is normal), you’re taking away almost all sugars too. As such, this can lead to dramatically reduced blood sugar levels. 

If you have Type 1 Diabetes, this could lead to low blood sugar levels or in extreme cases, a hypoglycemic episode, which has dangerous consequences and can lead to coma or death if left untreated.

In a study of diabetes patients who followed a ketogenic diet for 2 years, it was recorded that they experienced the symptoms of low blood sugar levels on average, once a day [3].

May lead to flu-like symptoms

In the immediate aftermath of starting with a ketogenic diet, you may find you experience flu-like symptoms which could knock you for six. 

This is actually quite common when you start on a ketogenic diet, as the sudden change in carb intake can be a shock to the system as your body adjusts [4], and can cause the following symptoms: 

  • Fatigue
  • Nausea 
  • Headaches
  • Constipation
  • Aches in the muscles

These symptoms will usually only last just a couple of weeks and it’s likely you’ll start to feel better as your body adjusts. However, keep an eye on how you feel over time and think about ensuring you’re drinking plenty of water and getting plenty of electrolytes in your diet [4]. 

May leave you nutrient deficient

Following on from the previous point, the keto diet can leave you feeling unwell if you’re not getting all the nutrients your body needs to function well. 

As you’re significantly cutting down a big section of your normal food intake, you’ll find that there will be nutrients you may struggle to gain without these foods in your diet. Especially if you haven’t planned and accounted for these changes in advance. 

Key, nutrient rich foods that might be restricted on your ketogenic diet include oats and grains, fruits like bananas and apples, and even legumes which may have some carbohydrate content. Obviously, if you rely on any of these foods in your normal day to day, removing them could also remove key vitamins and minerals your body needs to function. 

Studies focussing on similar low carb diets, such as the Atkins diet, have revealed that, on average, people are consuming just 12 of the 27 nutrients the body needs [5]. Over an extended period of time, this can lead to deficiencies. 

There are a couple of things you can do to ensure you don’t end up with a deficiency after starting on a keto diet. You can supplement your diet with specific vitamins, although a multivitamin may be more convenient

The key areas to be aware of are potassium, sodium, calcium, vitamins E, B and C [6].

Or, you can speak to your physician and consider where you think your deficiencies may lie, and research the foods you need to ensure you’re getting the right foods to support your body. 

May lead to constipation and stomach pain

When it comes to ensuring your body has a healthy and effective digestive system, fiber is the name of the game. However, so many fiber rich foods also come with a carbohydrate value too. 

For example, key high fiber foods that will help everything run smoothly in your digestive system include oats, grains, fruits and starchy vegetables. 

With only a restricted 50g or less of carbohydrates in your diet, it might be difficult to fit these high fiber foods into your keto diet and as such, you might experience the following symptoms: 

  • Constipation
  • Digestive pains
  • Stomach pains

May impair general bone health

There have been links between reduced bone health and strength during a ketogenic diet. 

There have been animal studies which have suggested that a prolonged ketogenic diet can reduce bone mineral density which in turn has led to a decrease in bone strength [7]. 

This is worth bearing in mind if you already have medical concerns about bone strength and density. 

Who shouldn’t do keto?

When asking if a keto diet is dangerous, it’s important to consider your current health. As outlined in the sections above, someone with diabetes, a chronic health condition or issues with bone strength and density shouldn’t do a keto diet as it could be dangerous to your health. 

If you are still considering a keto diet, we’d recommend consulting a medical professional before making any big changes to your food intake.  

How long can you stay on a keto diet safely?

If you don’t have any negative reactions or existing health issues, dieticians recommend doing keto for 3-6 months at a time as a maximum to avoid nutrient deficiencies as outlined above. 

If you do keto for longer than this, there is a risk that you could see longer term negative impacts if you’re not getting all the nutrients you need on this very restrictive diet. When evaluating is a keto diet dangerous, be sure to explore how long you intend to stick to it for, as it could become more concerning if you’re doing it for a long period of time. 

Are keto pills dangerous?

It’s worth being aware that taking keto pills can upset your stomach and digestive systems, and lead to bad breath and headaches. They can also cause an imbalance of your electrolyte levels which could impact body processes and the way you feel [8]. 

If you also have any of the health conditions listed above, it’s worth remembering that keto pills can also negatively impact these conditions and even make them worse. 

As such, it’s always worth considering speaking to your doctor before you start taking a supplement like a keto pill, or embarking on a ketogenic diet. 

Is a keto diet dangerous? Final summary

In short, a keto diet can be dangerous in a range of different circumstances. For example, if you have an existing health condition like weak bones or diabetes. If you undertake a keto diet for too long, it can also lead to electrolyte imbalances and nutrient deficiencies. 

As such, it’s important to remember to be cautious or consult your doctor before you commit to any drastic changes to your diet. 

The keto diet can be drastic as you’re essentially cutting out an important source of nutrients and energy. As such, we would urge all our readers to take a cautious approach and seek medical attention before making a big change like this. 


gymgirlfit was created by health and fitness enthusiasts, with backgrounds in powerlifting and writing. We've written for a number of well-known fitness publishing companies.

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