Can You Get Blurry Vision on Keto Diet?

Blurry Vision on Keto

The keto diet is renowned for its ability to produce significant and sustainable weight loss, for the way it balances blood glucose levels and for its ability to reduce cholesterol. Most people who adhere to the ketogenic diet do lose weight and enjoy many other benefits as well.

But a small number of people claim that after switching to a low carb diet they experience blurry vision. While the number of people claiming to experience this is small nothing to do with eyesight should be considered a minor issue. So we decided to take a look at these reports and see if it’s actually possible for the high fat keto diet to produce blurry vision.

The Science Behind Low Carb Diets and Eyesight

glasses with eye chart

It’s long been known that there is a link between blood glucose and eye function. This connection is one reason why so many people with diabetes wind up losing some or all of their sight.

Chronic high blood sugar is one of the most common side effects of poorly controlled diabetes, along with bad breath.

Increased glucose levels act like acid and can cause physical damage to the tiny veins of the retina. 

This, in turn, causes the retina to swell which affects both the center of a person's field of vision and their ability to see things clearly. This blurry vision in diabetics is a red flag, so proper diagnosis or treatment should never be postponed. It usually doesn’t take much more than a year for these adverse effects to manifest themselves as a permanent loss of sight.

Keep in mind that we are talking about diabetics here, just to provide an example of the link between high carb diets (which can wreak havoc on blood sugar) and eyesight. One of the great things about the low carb weight loss diet is that it does an outstanding job bringing blood glucose under control. And that is true both for diabetics and those who may have been on their way to developing Type II diabetes if they did not make the switch to the ketogenic diet.

Is Possible to Get Blurry Vision on Keto?

eyeglasses on chart

It is possible to get blurry vision while on the keto diet although, unless you are diabetic, the odds are slim that it will happen. That said, there are a couple of possible causes behind keto and blurry vision in non-diabetics. They are:

  • Hypoglycemia - Hypoglycemia occurs when glucose levels fall below the level necessary for your body to function normally. Symptoms can include shaking, clumsiness, confusion, hunger, sweating, and general weakness. In people on the keto diet hypoglycemia is often the result of sneaking carbs on the side. When people allow themselves a “cheat day” they often go overboard. In the aftermath they experience high concentrations of blood sugar followed several hours later by those blood sugars crashing dramatically. This is called "reactive hypoglycemia." Whether you are diabetic or not this quick swing in blood glucose can affect the tiny veins in the retina and cause the type of blurring we detailed above.
  • Thiamine deficiency - An important Australian study done nearly 40 years ago [1] noted that some people on the ketogenic diet suffered from optic neuropathy. Optic neuropathy is a loss of central or peripheral vision due to damage to the optic nerve. When these patients underwent treatment with thiamine supplements, their eye problems cleared up completely. The researchers in that case also recommended vitamin B supplements to fend off any future problems. If you suffer from blurred eyesight, fatigue or muscle cramps, it may indicate a thiamine deficiency.

Can the Keto Diet Actually Improve Your Vision?

vision from scrabble letters

The keto diet can improve your vision, prevent future eye problems and prevent acute problems from becoming worse, particularly for diabetics. Here are a couple of reasons why the keto diet may actually improve your eyesight:

  • Eliminating dangerous carbs reduces the potential for macular degeneration - A study by Tufts University concluded that Age-related Macular Degeneration (AMD) can in many cases be linked directly to eating carbohydrates with a high glycemic index rating [2]. That includes things like pasta, white rice, and bread. In other words, the kind of foods rich in carbs and calories most people eat before they switch to the weight loss keto diet. Once on the ketogenic diet these foods are mostly, if not completely, eliminated from their diet and the risk of developing AMD reduces drastically. Also, avoiding these dangerous carbs can prevent new episodes of reactive hypoglycemia.
  • Stabilizing blood glucose helps prevent glaucoma - Stabilizing blood sugars also helps slow or prevent glaucoma in diabetics and may help stave off glaucoma in non-diabetics. According to a study published by the NIH [3], one of the side effects of the keto diet is that it helps protect the cells of the retina from sugar-driven degeneration as well as mitochondrial diseases of the eye. Mitochondrial disease can cause atrophy of the optic nerve as well as disruption of peripheral eyesight.

A lot of the health benefits for your eyes that are available through the keto diet are ones you won't notice. After all, it's difficult to quantify something that doesn’t happen. If you take the keto diet to heart and you don't develop AMD, you'll know what we're talking about.

Final Summary:

As Katherine Brooking, MS, RD writes over at

Numerous studies show that what’s most important for long-term weight loss success is adherence, so if you can’t stick with a plan for life, it’s probably not going to give you the results you want.

Katherine Brooking,

That goes for the keto diet as well as any other diet plan you adopt for losing weight.

In order to reap the eye-related benefits of the keto weight loss diet, you need to stick to a daily carbohydrate intake of 20 grams and, most importantly, avoid those cheat days that can lead to dangerous blood sugar crashes. If you have any questions or concerns about the effect of the keto diet on your eyes, seek advice, diagnosis or medical advice from your eye care professional.


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