The first weeks of a ketogenic diet can bring questions about sleep, digestion, energy and exercise. Use this guide to find the symptom you are concerned about, understand the adjustment described by our clinical team, and identify what to discuss with your medical provider.
What to expect during the adjustment
One of the goals of a ketogenic diet is to get into a state of “ketosis”, which means ketones are your body’s main fuel source instead of sugar. Most people will enter ketosis within a few days of starting a ketogenic diet, but it can take longer for your body to fully adapt to this new state of fat burning. This is one of the reasons we really do not focus on weight loss in the first 4-6 weeks of starting a ketogenic diet.
There are other complex adaptations that occur over the course of several weeks to months that can also vary on timing depending on the individual. One example is that our kidneys will “learn” to hold on to ketones: the rate of ketone loss in urine 3 weeks into the diet will be ⅓ of that when you started.
Another example, which will be discussed in more detail below, is exercise performance and tolerance.
The majority of side effects require no or minimal intervention. However, as they can be unpleasant, we still aim to proactively mitigate some of them from the get-go. Remember that all articles like this are written to provide high level overviews and should be used for informational purposes only. You are unique, please discuss any symptoms you develop with your medical provider.
Keto-flu symptoms
Keto-flu symptoms can be broad but may include lightheadedness/dizziness, fatigue, insomnia, irritability, headaches, difficulty concentrating/brain fog, constipation, and nausea. This is usually the result of not eating enough sodium and/or drinking enough water. The guidance here focuses on symptoms during the adjustment period. For the detailed discussion of sodium, potassium and magnesium, see Electrolytes & Keto.
Keto-flu may be prevented by drinking enough water/unsweetened tea/coffee/seltzer until your urine is mostly clear while trying to get a minimum of 5 grams of sodium per day (approximately 1.5 teaspoons), with some people benefiting from up to 7 grams of sodium per day (2 to 3 teaspoons of salt). Speak with your doctor before implementing these suggestions if you suffer from Heart Failure, Kidney Disease, or Hypertension. If you are suffering from keto-flu despite this, adding an additional 1-2 grams of sodium per day may resolve your symptoms. Many in long-term ketosis find that 5g of sodium per day is ideal, not just during the first few weeks as you adapt.
The required amount of sodium could be even higher if you do anything that causes significant sweating during the day. This can be achieved through your diet or through diet plus additional supplementation. Food and supplement examples are collected in the sodium section of Electrolytes & Keto.
Exercise during the adjustment
Even more reason to add extra salt to help mitigate the keto-flu! Also, to help avoid muscle fatigue, you can take ½ teaspoon of salt within 30 minutes to 1 hour before exercising. If you find yourself feeling more sluggish than usual during the first 5-15 minutes of hard exercise, then drinking 1-2 cups of water five minutes before starting can help.
When to discuss sodium with your clinician
Most importantly, if you have one of the following conditions then you must speak with your medical provider to find out what a safe level of salt consumption is for you:
- Heart failure
- Kidney disease
- Hypertension
Muscle cramps
In general, this is typically from not enough magnesium, sodium, potassium, water, or a combination of them all. Adequate hydration / sodium as discussed above under the Keto-Flu section can help decrease the risk of cramps. If you still suffer from muscle cramps despite adequate sodium and water intake, the below protocol from Dr. Phinney can be helpful for people. If it is primarily in your calves at night time, then stretching 4x per day or at least before going to bed can also help reduce symptoms.
Take 3 slow-release mg tablets daily for 20 days (Slow-Mag brand, Mag-64 or Mag-Delay). Most cramps stop within 2 weeks of starting slow-mag tablets. However, you should continue taking the supplement for 20 days.
If cramps return, take the supplement again for 20 more days, and then continue taking one tab per day.
If the cramps still return, increase to 2 tabs per day (do not do this without your medical provider’s supervision if you have kidney disease.)
The Electrolytes & Keto guide provides more background and product information. The original electrolyte resource is also retained for reference.
Irritability and carbohydrate cravings
Food addiction exists. Just as you can withdraw from caffeine, alcohol, or other drugs, you can also withdraw from carbohydrates and processed foods. These symptoms will typically subside over the first few days to weeks. Over the long term, you can imagine it is like a dial that is intermittently turned up, but decreases over time so it no longer is noticeably impacting your life.
Hair loss
This side effect is actually not specific to the ketogenic diet, but to some forms of weight loss in general. For example, in a study of individuals who had a sleeve gastrectomy (bariatric surgery), 72% of participants had hair loss following the surgery.
The hair loss started 3-4 months after surgery and lasted for an average of 5.5 months. Of note, biotin supplementation did not do anything to improve the speed of hair regrowth. Almost all cases resolve within one year. You may notice this as early as 2 months. New hair typically starts to regrow 2-3 months later.
This type of hair loss is called telogen effluvium. It can occur from any kind of major life stressor, both mental and physical (trauma, childbirth, surgery, etc.). Additional causes include too few calories or protein, and deficiencies in zinc, iron, essential fatty acid and selenium.
Insomnia
Insomnia may occur for a number of reasons when first starting a ketogenic diet. As stated above, it can be a symptom associated with keto-flu. If insomnia does become one of your symptoms, following the above recommendations on hydration and electrolytes may resolve it. However, even if it doesn’t, it will usually resolve on its own within a few weeks as your body adapts to the new lifestyle. If things are persisting, make sure to follow up with your medical provider. There are even some studies that have shown improvements in sleep once on a ketogenic diet.
Another cause of insomnia can be nocturia – or having to pee during the night. This can occur as your insulin levels drop, causing your kidneys to pee out more water and electrolytes.
Additionally, some people just report more energy throughout the day and night when they are on a ketogenic diet. If you just feel more awake at bedtime, you can try increasing physical activity earlier on in the day to help make you more sleepy at bedtime. Sometimes adding in some non-starchy vegetables like broccoli, cauliflower, okra, brussel sprouts etc. to your dinner can help improve insomnia.
Other tips to help with insomnia and optimize sleep can be found in the Weight Loss Curriculum → Our Approach to Lifestyle: The Levers → Sleep Lever. For a brief overview, see below:
- Follow a nightly routine that is calming (ex. Reading a book, warm shower, mindfulness/meditation)
- Try to avoid screens at least one hour before bedtime. You can use Flux or other apps to decrease the blue light emitted from your devices and also get blue light blocking glasses to use in the few hours before bedtime.
- Avoid alcohol a few hours before bed. Alcohol may help you initially fall asleep, but will greatly impact the quality of your sleep.
- Avoid caffeine in the afternoon or evening as that can also impact your ability to fall asleep as well as the quality of your sleep.
- Try to avoid eating a few hours before bed.
- Keep your room cool and dark.
Diarrhea, constipation and bloating
There are several causes of diarrhea when transitioning to a ketogenic diet. It is important to discuss this with your medical provider if (1)it is severe; (2)there is blood in it; (3) it is not resolving after more than one week; (4)or it is causing dehydration.
The typical causes are sugar alcohols (xylitol, sorbitol, mannitol, maltitol, isomalt) or other artificial sweeteners, certain types of fats, excess protein, and medications.
Certain people are more susceptible to gastrointestinal (GI) side effects from sugar alcohols and artificial sweeteners that are found in low-carb replacements (drinks, candies, protein bars, etc). If you add in lots of replacement foods and start having diarrhea, bloating, or nausea, you may want to cut back and see if it resolves.
We have also seen patients who previously tolerated metformin suddenly stop tolerating it after starting a ketogenic diet. Once stopping the metformin, the symptoms resolve. Again, this is trial and error. However, please speak to your doctor before stopping any prescribed medications.
Less commonly, people may consume so much protein (typically more than 20% of total calories) that the protein itself causes diarrhea. Additionally, some people seem to be sensitive to excess quantities of soybean, corn, or other vegetable oils. Again, you are unique and a big piece of a ketogenic diet for all people is trial and error – learning what works best for you!
Constipation, on the other hand, typically occurs from dehydration and too little sodium intake, rather than too little fiber intake (as people often believe). Some people may mistake less frequent bowel movements for constipation; if they space out but are still a normal consistency and easy to pass, you are likely not constipated. Simply ensuring 2 liters of water intake and adding an LMNT, 2 cups of broth, or a bouillon cube with 1 gram of sodium will often resolve this symptom. Additionally, sometimes it just takes the gut a little time to adapt to the new diet (especially if you are adding in a lot of new foods), in which case this resolves on its own. If it persists, you could try adding 1 teaspoon of magnesium citrate.
Gout
There is a short-term increased risk of gout flares when starting a ketogenic diet. This occurs due to the kidneys temporarily decreasing excretion of uric acid. In the Virta health study, average uric acid levels increased at 70 days, but were back to their baseline by one year (and typically by 3 months). Moreover, no new cases of gout were diagnosed despite this increase in uric acid levels. The long-term risk of gout actually decreases.
If you suffer from recurrent gout flares, it would be prudent to discuss starting a prophylactic medication or having medication in hand before starting a ketogenic diet in case you do have a gout flare.
Kidney stones
Some risk factors for kidney stones include genetic predisposition, dehydration, and low dietary magnesium. As discussed above, uric acid may increase in the first few months of a ketogenic diet due to decreased excretion from the kidneys. However, in the Virta health study with over 200 patients being studied for two years, there were no new cases of kidney stones. The emphasis on adequate hydration and electrolytes may be the reason for their results. In a systematic review and meta-analysis, there was a 5.9% incidence of kidney stones after an average follow up of 3.7 years. In the general population, the 12-month incidence of kidney stones was 2.1% and the prevalence at any given time was 11%.
Keto rash
We have never seen “keto rash”. However, it has been reported elsewhere. It typically occurs early on in those who have had rapid weight loss. People who have developed this report that it resolved when adding some carbohydrates back in. Some people are then able to resume a ketogenic diet with a more mild rash and even maintain ketosis without recurrence. If you are concerned that you developed a “keto rash”, you should discuss this with your provider.
Changes in exercise performance
You may or may not notice this, depending on how active you are before starting this lifestyle. For those who are very active and used to consuming larger quantities of carbohydrates, this may be more noticeable. It may take a few weeks to a few months to feel like you are back to doing vigorous exercise at your pre-keto performance. Prior studies from Dr. Phinney have shown that muscle glycogen stores drop to about half of their prior level after 4-6 weeks on a very low-carb, high-fat diet. In a longer study of highly trained individuals, however, glycogen muscle stores were normal for individuals who had followed a ketogenic diet for more than 6 months. The take-away is to give your body time to adapt to this new way of living.
Eating without a gallbladder
Although some people report difficulty with a high-fat ketogenic diet, the reality is that many people without a gallbladder do just fine. If you do have issues with the higher fat content of this lifestyle, one solution is to try to have smaller quantities of fat at a given time, rather than large quantities in a single meal. Additionally, some people have less issues with certain types of fat such as cream or greek yogurt, so you can play around and see if there are specific kinds that mess with you.
References
- Acharya P, Acharya C, Thongprayoon C, et al. Incidence and Characteristics of Kidney Stones in Patients on Ketogenic Diet: A Systematic Review and Meta-Analysis. Diseases. 2021;9(2):39. https://doi.org/10.3390/diseases9020039
- Athinarayanan SJ, Adams RN, Hallberg SJ, et al. Long-Term Effects of a Novel Continuous Remote Care Intervention Including Nutritional Ketosis for the Management of Type 2 Diabetes: A 2-Year Non-randomized Clinical Trial. Frontiers in Endocrinology. 2019;10. Accessed January 27, 2023. [https://www.frontiersin.org/articles/10.3389/fendo.2019.00348] (https://www.frontiersin.org/articles/10.3389/fendo.2019.00348)
- Féry F, Balasse EO. Ketone Body Production and Disposal in Diabetic Ketosis: A Comparison with Fasting Ketosis. Diabetes. 1985;34(4):326-332. doi:10.2337/diab.34.4.326
- Hill AJ, Basourakos SP, Lewicki P, et al. Incidence of Kidney Stones in the United States: The Continuous National Health and Nutrition Examination Survey. Journal of Urology. 2022;207(4):851-856. doi:10.1097/JU.0000000000002331
- Phinney SD, Bistrian BR, Wolfe RR, Blackbiurn GL. The human metabolic response to chronic ketosis without caloric restriction: physical and biochemical adaptation. Metabolism 32:757-768.14. Volek JS, Freidenreich DJ, Saenz C, Kunces LJ, Creighton BC, Bartley JM, Davitt PM, Munoz CX, Anderson JM, Maresh CM, Lee EC, Schuenke MD, Aerni G, Kraemer WJ, Phinney SD. Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism. 2016; 65:100-1015.
- Şen O, Türkçapar AG. Hair Loss After Sleeve Gastrectomy and Effect of Biotin Supplements. J Laparoendosc Adv Surg Tech A. 2021;31(3):296-300. doi:10.1089/lap.2020.0468
- Volek JS, Phinney SD, Kossoff E, Eberstein J, Moore J. The Art and Science of Low Carbohydrate Living: An Expert Guide to Making the Life-Saving Benefits of Carbohydrate Restriction Sustainable and Enjoyable. Lexington, KY: Beyond Obesity; 2011.
