Who should not fast

Every religious tradition covered on this site already contains exemptions from fasting, and they exist for good reasons that predate any medical literature. This page sets out who those exemptions usually cover and what the specific physical risks are — so that the conversation with your family, your tradition and your doctor starts from real information rather than guesswork.

Pregnancy and breastfeeding

Pregnancy raises fluid requirements and lowers the body's tolerance for going without carbohydrate, and dehydration in pregnancy can reduce amniotic fluid and trigger contractions. A long dry fast — Karva Chauth, Nirjala Ekadashi, Chhath, Hartalika Teej, a summer Ramzan day — carries the most risk.

Breastfeeding adds a further fluid and energy demand on top, and milk supply is sensitive to dehydration.

Every tradition described here recognises this. Islamic law provides explicit exemption with qada or fidya; Hindu families routinely accept a modified or partial observance; Jain guidance is given according to capacity. This is not a matter of asking permission to break a rule — the provision already exists. What it needs is a conversation with your doctor and with your family, in advance.

Diabetes — especially on insulin or sulfonylureas

This is the highest-risk group on this page, and the risk is specific. Insulin and sulfonylureas (glimepiride, gliclazide, glibenclamide and similar) lower blood glucose whether or not you have eaten. Miss the meal the dose was matched to and hypoglycaemia becomes a real possibility — and a severe hypo is a medical emergency, not an inconvenience.

Metformin, DPP-4 inhibitors and most newer agents carry much lower hypoglycaemia risk, but SGLT2 inhibitors add a dehydration and ketosis concern during a dry fast, which is a different problem again.

The correct step is a consultation BEFORE the observance, not during it. Doses and timings are routinely adjusted so that people can fast — Ramadan in particular has established risk-stratification guidelines used by doctors worldwide. Many people with diabetes fast safely with an adjusted regimen. Some are advised not to. Only your doctor can tell you which you are.

If you fast and experience shaking, sweating, confusion, palpitations or sudden weakness, treat it as hypoglycaemia and take sugar immediately. In Islamic practice, breaking the fast in this situation is explicitly permitted; in Hindu and Jain practice, no tradition asks anyone to risk collapse.

A history of disordered eating

Fasting structures — long windows, restart rules, counting days, restricted food lists — closely resemble the mechanics of restrictive eating, and for someone with a history of anorexia, bulimia or binge eating they can reactivate it while looking outwardly like devotion.

The signals worth taking seriously are: relief at not eating rather than difficulty with it, extending a fast beyond what the observance asks, secrecy about food, and a preoccupation with the numbers on a page like this one.

If any of that is familiar, talk to someone before undertaking a long or repeated fast. This site publishes calorie figures, and that is exactly the kind of information that is useful to most people and unhelpful to some.

Children

Children have smaller glycogen stores, higher fluid turnover relative to body size, and less ability to recognise or report early dehydration. Traditions handle this the same way across the board — children are generally not expected to keep full fasts, and where they participate it is usually partial and supervised.

A child who wants to join in a family observance can usually do so in a shortened or modified form. What is not appropriate is a full dry fast in heat.

Older adults

Thirst sensation declines with age, so older adults dehydrate further before feeling thirsty. Add commonly prescribed diuretics, blood-pressure medication and reduced kidney reserve, and a long dry fast becomes a meaningfully higher risk than the same fast at 30.

Dizziness on standing and falls are the practical hazard, and a fall in an older adult is not a minor event.

Anyone on regular medication

• Medicines that must be taken with food — many will cause nausea or stomach irritation on an empty stomach, and some are absorbed poorly without it.
• Diuretics — they increase fluid loss at precisely the wrong moment.
• Blood-pressure medication — the combination with dehydration causes dizziness on standing.
• Lithium and some anti-epileptics — blood levels shift with hydration status, and the therapeutic window is narrow.
• Anticoagulants and medicines with strict timing — a shifted eating window shifts the schedule with it.
• The point is not to stop any of these. It is that a fast changes when and whether you can take them, and that is a question for your prescriber, once, in advance.

Other conditions worth a specific conversation

• Kidney disease or a history of kidney stones — dry fasting concentrates urine considerably.
• Heart failure — fluid balance is being actively managed and a fast interferes with it.
• Migraine — long fasts and caffeine withdrawal are two of the most reliable triggers there are.
• Recent surgery, active infection or recovery from illness — the body is already in deficit.
• Peptic ulcer or severe reflux — long empty periods followed by a large fried meal is the worst possible pattern.
• Gout — dehydration raises uric acid concentration and can precipitate an attack.

When to stop, whatever the observance

Stop and seek help for: fainting or near-fainting, confusion or slurred speech, chest pain, a headache that will not clear, vomiting that will not stop, an inability to stand, or — in heat — skin that has stopped sweating.

No tradition described on this site treats collapse as devotion. Every one of them has a way to make up or make good a fast that could not be completed.

SOURCE·Published vrat traditions + IFCT 2017·figures given as ranges; what is and is not sourced is set out in full on the sources page·REVIEWED JUL 2026

Sources, with dates →