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Medical Disclaimer
Important safety information about fasting, contraindications, and the limits of this Service.
Last updated: 8 June 2026
Not medical advice
SardinesFasting is educational and for self-experimentation only. It is not medical advice and not a substitute for care from a licensed professional. Talk to your doctor before starting any fasting protocol.
Do not fast without medical supervision if you are
- Pregnant or breastfeeding.
- A child or adolescent (under 18 — growing bodies).
- Someone with a history of any eating disorder.
- Living with type 1 diabetes, or type 2 diabetes on insulin or sulfonylureas.
- At a BMI under 18.5.
- Living with active gallbladder, kidney or liver disease.
- Taking medication that requires food, or any prescription that doses around a fed/insulin state.
- Living with adrenal insufficiency or untreated thyroid disease.
Watch-outs during a fast
- Electrolytes — especially past 24h. Add sodium, potassium and magnesium. Lightheadedness on standing usually means you need salt and water.
- Refeeding syndrome — risk grows the longer the fast. The 5-day and 21-day protocols require a slow, protein-led refeed.
- Medication interactions — many medications dose around a fed state. If you take any prescription, speak to the prescriber before an extended fast.
Stop the fast immediately and seek help if you experience
- Persistent chest pain, severe shortness of breath, or palpitations.
- Fainting or near-fainting.
- Severe disorientation or confusion.
- Severe abdominal pain.
- Vomiting that will not stop.