How to break a fast — your plan

You fasted: 5 days or longer · Five days and beyond.

Break this one with medical supervision. This page will not give you a meal plan for it.

How well this is known: Refeeding syndrome and its management are guideline material. That is the strongest evidence on this page, and it is the one band where the answer is not a meal.

Break a fast of this length with medical supervision

There is no meal plan on this sheet, and that is deliberate. Past five days the guideline stops being about what to eat and becomes an energy figure per kilogram of body weight, bloods measured before the first mouthful, and thiamine given before feeding rather than after. Talk to a clinician before you fast, not before you eat again.

NICE CG32, recommendation 1.4.5: “People who have eaten little or nothing for more than 5 days should have nutrition support introduced at no more than 50% of requirements for the first 2 days, before increasing feed rates to meet full needs if clinical and biochemical monitoring reveals no refeeding problems.”

What supervision involves:

Potassium, phosphate and magnesium are measured before feeding starts, and daily once it has.
Feeding restarts at a MAXIMUM of 10 kcal per kilogram of body weight a day — as little as 5 where the case is extreme — and is built up to full needs over 4 to 7 days.
Thiamine is given immediately before feeding and through the first 10 days, at 200 to 300 mg daily under the British guideline and 100 mg before feeding under the American one.
Potassium, phosphate and magnesium are supplemented from the start rather than corrected first.

Avoid at first

A sugary drink or dessert as the first thingThe one avoid line that applies at every band, and not for the reason usually given: the longer the fast, the BIGGER the glucose rise from the same carbohydrate, because a fast lowers insulin sensitivity rather than raising it. It is a spike, not a crash. Nothing about it is dangerous in a healthy person; it is simply the most pointless way to spend the first thing you eat.
Eating until you are full because you earned itThe hunger after a long fast overshoots what you need, and it does not stop being hunger when you have had enough. Stop while you could still eat more.
AlcoholOn an empty stomach after a long fast it arrives faster and hits harder, and it is a poor first thing to ask a quiet gut to process.
A large raw salad, or raw cruciferous vegetablesRaw fibre is the hardest thing there is for a gut that has spent a day doing nothing. Bloating and cramps, reliably. Cook them and they are fine.
Deep-fried or heavily processed foodHard work to digest at the best of times, and this is not the best of times.
A large portion of nuts or seedsDense, fatty and full of fibre. A handful in a meal is fine; a bowl of them as the first food is not.
A big glass of milk or a large serving of unfermented dairyLactose tolerance is a spectrum, and a large dose of it as the first food after a day is how people who did not know they were at the sensitive end find out.
A large, fatty mealFat slows the stomach down. That is useful when you are eating normally and unhelpful when the stomach is already slow.
Making up the missed calories in one sittingThe day is the unit past 36 hours, not the meal. Spreading the food out is the single most useful thing on this list.
Going straight back to your normal trainingGive it a day. Hard training on the first day back stacks a second demand on top of the one your body is already dealing with.
Caffeine on top of the first mealCoffee lifts colon motor activity within minutes, which is not what a gut coming back from three days needs on top of food.

Refeeding risk — the criteria clinicians work from

This checklist is about the state you were already in, not about the length of one fast. Read it before you fast rather than before you eat again. Any one of the first list, or any two of the second, and this belongs with a clinician rather than a web page.

Any ONE of these

BMI less than 16 kg/m²
Unintentional weight loss greater than 15% within the last 3 to 6 months
Little or no nutritional intake for more than 10 days
Low levels of potassium, phosphate or magnesium before feeding

Or any TWO of these

BMI less than 18.5 kg/m²
Unintentional weight loss greater than 10% within the last 3 to 6 months
Little or no nutritional intake for more than 5 days
A history of alcohol abuse, or drugs including insulin, chemotherapy, antacids or diuretics

Stop and get medical help if, after you start eating again, you become confusion, or difficulty thinking clearly; breathlessness; a racing or irregular heartbeat; fainting, or feeling close to it; swelling in the legs or ankles after you start eating again. None of those is a symptom to push through.

Portions are rules of thumb, not measurements. No study has established the right first-meal size after any length of fast, and this sheet says so rather than printing a figure it cannot defend. What is reliable is the direction of the error: people overshoot. Stop while you could still eat more.

Never skip, delay or adjust medication to protect a fast. If a medicine needs food, the food wins. Nothing on this sheet is medically reviewed; every guideline figure on it names the guideline it came from.

getfasted.app/tools/how-to-break-a-fast — every length, with the reason behind each step. Not medical advice.