Keto Diarrhoea: Causes and Fixes

Starting a ketogenic diet often brings digestive changes, with diarrhoea being a frequent but manageable side effect. The shift to very low carbohydrate intake alters gut microbiota and electrolyte balance, particularly in the first weeks. This article examines the mechanisms behind keto diarrhoea and provides practical solutions grounded in clinical research.

Why diarrhoea occurs on keto

When carbohydrate intake drops below 50g daily, the body undergoes several physiological changes. The rapid excretion of water that accompanies glycogen depletion can lead to temporary electrolyte imbalances. Sodium, potassium and magnesium levels may drop, affecting intestinal motility. A 2013 study in the British Journal of Nutrition noted that very-low-carbohydrate diets induce distinct changes in gut microbiota composition within days (Bueno et al., 2013).

Electrolyte management strategies

Proper electrolyte supplementation proves crucial. An adult on keto typically needs:

3,000–5,000 mg sodium
3,000–4,000 mg potassium
300–500 mg magnesium

Tesco sells Lo Salt (66% potassium chloride) for £1.85 per 125g shaker, while Morrisons stocks magnesium citrate tablets for £4.50 per 100 capsules. Bone broth made with 1 tsp salt provides approximately 2,300 mg sodium per mug.

What this means in practice

UK keto practitioners often find autumn and winter easier for managing hydration. The NHS recommends gradual dietary changes rather than abrupt shifts. keto flu symptoms typically resolve within weeks, while optimal magnesium supplements help maintain regularity. For those struggling with meal planning, the Keto Dieting app tracks electrolytes alongside macros.

Frequently asked questions

{“question”: “How long does keto diarrhoea last?”, “answer”: “Most people experience improvement within 2-3 weeks as the gut adapts. Persistent symptoms beyond a month warrant medical review, particularly if accompanied by dizziness or muscle cramps.”}

{“question”: “Can certain keto foods make diarrhoea worse?”, “answer”: “Yes. Sugar alcohols like maltitol in keto treats, excessive MCT oil, or sudden increases in leafy greens can exacerbate symptoms. Introduce high-fibre foods gradually.”}

{“question”: “Should I stop keto if diarrhoea persists?”, “answer”: “Not necessarily. Try reducing fat intake temporarily, ensuring adequate electrolytes, and eliminating potential irritants. Chronic diarrhoea may indicate underlying conditions unrelated to diet.”}

The bottom line

Keto diarrhoea usually stems from electrolyte imbalances and gut microbiome shifts during carbohydrate restriction. Strategic sodium, potassium and magnesium intake, alongside gradual dietary changes, typically resolves symptoms. Those with pre-existing digestive conditions should monitor symptoms closely. If you’d rather not do the macro maths yourself, the Keto Dieting app does it for you on Google Play and the App Store.

Educational only — not medical advice. This article is for general information. Speak to your GP before changing your diet, especially if you have type 1 or type 2 diabetes, kidney or liver disease, are pregnant or breastfeeding, or take medication for blood pressure, cholesterol, or blood glucose.

References

Bueno NB, de Melo IS, de Oliveira SL, da Rocha Ataide T (2013). Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. British Journal of Nutrition. https://doi.org/10.1017/S0007114513000548
Paoli A, Rubini A, Volek JS, Grimaldi KA (2013). Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. European Journal of Clinical Nutrition. https://doi.org/10.1038/ejcn.2013.116