Intermittent fasting is not suitable for everyone. Before choosing an eating window or planning a longer gap between meals, consider your health, medication, nutritional needs and relationship with food.
Some people should avoid fasting for weight management. Others need an individual assessment and a clear plan from their healthcare team before changing meal timing.
Children and teenagers, pregnant or breastfeeding women, and people with a history of eating disorders should avoid intermittent fasting for weight management. People with diabetes—particularly those using insulin—need specific medical guidance rather than a self-directed fasting plan.
This guide explains the main concerns and helps you prepare useful questions for a clinician. It cannot determine whether fasting is safe for you personally.
A Quick Guide to Who Should Avoid Fasting
The distinction between “avoid fasting” and “seek individual medical advice” matters. A general online schedule cannot resolve either situation.
| Situation | Appropriate next step |
|---|---|
| Under 18 | Avoid weight-loss fasting; seek age-appropriate nutritional advice |
| Pregnant or breastfeeding | Avoid intermittent fasting for weight management |
| Current or previous eating disorder | Avoid self-directed fasting and speak with your treatment team |
| Type 1 diabetes, especially when using insulin | Do not begin a self-directed fasting routine |
| Type 2 diabetes or glucose-lowering medication | Obtain an individual medication, monitoring and meal plan first |
| Frailty or difficulty meeting nutritional needs | Seek a clinical nutrition assessment |
| Other ongoing medical conditions or medication requirements | Ask your clinician or pharmacist before changing meal timing |
These groups reflect concerns identified by Johns Hopkins Medicine and JAMA’s patient guidance. The list is not exhaustive, and being outside these categories does not establish that fasting is suitable for you.
If you are still learning the terminology, our intermittent fasting guide for beginners explains the different approaches. Suitability should come before choosing between them.
Children and Teenagers Should Not Follow Weight-Loss Fasting Plans
Adult fasting advice should not be adapted for a child by simply shortening the fasting window.
Johns Hopkins lists children and teenagers under 18 among those who should not try intermittent fasting.
If a young person has concerns about weight, eating or body image, arrange an assessment with a suitable healthcare professional. The advice should account for their age and circumstances.
Parents should also avoid presenting skipped meals or longer fasting periods as achievements. A young person does not need to copy an adult’s eating schedule because that schedule is followed elsewhere in the household.
Pregnancy and Breastfeeding Are Reasons to Avoid Weight-Loss Fasting
Pregnancy and breastfeeding call for individual nutritional care. They are not appropriate times to begin an online intermittent fasting program for weight management.
Both Johns Hopkins Medicine and JAMA advise against intermittent fasting during pregnancy and breastfeeding.
If you are concerned about weight changes, appetite or meal timing during either stage, discuss those concerns with your maternity team or another qualified clinician.
Religious fasting is a separate question that also deserves individual advice. Guidance about a commercial weight-loss program should not be used to decide whether a particular religious practice is medically appropriate.
A History of Eating Disorders Matters
An eating-disorder history remains relevant even when someone feels that their current eating is stable.
Johns Hopkins warns that strict fasting windows can trigger or worsen restrictive or obsessive eating behaviours in people with a history of eating disorders. JAMA also advises against fasting for people with, or at risk of, eating disorders.
Do not assume that describing a routine as “flexible” removes that concern.
Consider discussing the following experiences with a qualified professional:
- Feeling compelled to compensate for a meal by extending the next fast.
- Becoming increasingly anxious about eating outside a set window.
- Measuring success mainly by how long you can avoid food.
- Hiding food restriction from people close to you.
- Repeatedly alternating restriction with episodes of overeating.
These examples are prompts for seeking support, not a diagnostic checklist. You do not need to diagnose yourself before asking for help.
Our article on intermittent fasting mistakes discusses practical problems with fasting routines. When restriction or distress is involved, however, changing the timetable alone may not address the underlying concern.
Diabetes Requires Particular Care
Diabetes is a strong reason to avoid experimenting with fasting without medical guidance.
The US National Institute of Diabetes and Digestive and Kidney Diseases explains that skipping or delaying meals, or fasting while continuing certain glucose-lowering medicines, can increase the risk of low blood glucose. Insulin, sulfonylureas and meglitinides are among the medicines associated with this risk.
If You Have Type 1 Diabetes
Do not begin a self-directed fasting plan. Johns Hopkins specifically identifies people with type 1 diabetes who take insulin as a group who should not try intermittent fasting because of concerns about hypoglycaemia.
An internet article cannot provide the individual assessment required for decisions about insulin, food intake and monitoring.
If You Have Type 2 Diabetes
A diagnosis of type 2 diabetes does not provide a simple yes-or-no answer about fasting.
Before changing meal timing, ask your diabetes team:
- Could my current medicines cause low blood glucose?
- Would my existing treatment plan need adjustment?
- When should I check my glucose?
- What readings or symptoms mean I must stop?
- What should I do if I become unwell?
Do not reduce, skip or reschedule prescribed medication yourself to make a fasting window possible.
A program’s instructions cannot replace your diabetes management plan.
Frailty and Difficulty Meeting Nutritional Needs
Age alone is not enough to decide whether fasting is appropriate. Frailty and the ability to meet nutritional needs are more useful concerns to raise during an assessment.
JAMA advises against intermittent fasting for frail older adults and recommends discussing nutritional adequacy with a nutrition professional before starting a fasting diet.
If you are already struggling to eat enough, losing weight unintentionally or finding meals difficult, seek advice about those problems before restricting eating opportunities.
The first task is to understand why eating or weight has changed. A fasting timetable does not answer that question.
Other Health Conditions and Medicines Need Individual Review
People with ongoing medical conditions should discuss potential benefits and risks with their clinician before trying intermittent fasting. JAMA’s guidance specifically recommends this discussion.
Bring a complete medication list, including non-prescription products and supplements. Explain the actual routine you are considering.
“I want to fast” is less informative than:
“I am considering moving my first meal to midday and finishing dinner at 8 p.m. Would that conflict with my treatment or nutritional needs?”
Ask your pharmacist about instructions that require a medicine to be taken with food. Do not assume that a drink or a small bite meets the requirement for every medication.
The answer may depend on your particular medicine and treatment plan.
A Shorter Fasting Window Is Not Automatic Clearance
Someone who should avoid fasting should not treat a shorter window as a workaround.
Likewise, a person who needs a medication review still needs that review before choosing a different schedule.
The same principle applies when comparing 24-hour fasting with fasting once a week or fasting twice a week. Changing frequency or duration does not resolve a medical contraindication.
These guides explain how schedules differ. They do not provide individual permission to follow them.
Symptoms Should Prompt Action, Not a Longer Fast
Hunger is not the only experience to consider when evaluating a fasting routine.
JAMA identifies possible side effects including weakness, dehydration, headache, difficulty concentrating, low blood pressure and fainting. Johns Hopkins advises contacting a doctor about unusual anxiety, headaches, nausea or other symptoms after starting fasting.
Do not interpret worsening symptoms as proof that a program is working.
Stop the fast if you feel unwell, and seek advice appropriate to the symptoms. Fainting, confusion, severe weakness or symptoms that prevent you from functioning normally deserve prompt assessment.
Our guide to intermittent fasting side effects discusses this subject in more detail.
If You Have Diabetes and Suspect Low Blood Glucose
Follow your established hypoglycaemia treatment plan immediately. Treating low glucose takes priority over completing a fasting interval.
NIDDK advises people with diabetes to check glucose when symptoms occur and treat readings below their target or below 70 mg/dL. Severe episodes may leave someone unable to treat themselves and require emergency assistance.
If you do not already have a clear plan for recognising and treating low glucose, ask your diabetes team for one before considering changes to meal timing.
Does Buying a Fasting Program Make It Safer?
A paid program may explain its method, but purchasing it does not establish medical suitability.
This applies to Eat Stop Eat as well as other fasting products. Before evaluating a program’s schedule or convenience, resolve any concerns about health, medication or eating-disorder history.
Our Eat Stop Eat review examines the program’s approach and practical demands. It should be read as product information rather than individual medical advice.
A testimonial from someone of a similar age or weight cannot tell you whether the same routine is appropriate for you.
Questions to Take to Your Healthcare Appointment
You can make an appointment more useful by bringing a specific proposed schedule and a short list of concerns.
Ask:
- Is deliberate fasting appropriate for me at all?
- Do my medicines require particular meal timing?
- Could this routine make it harder to meet my nutritional needs?
- Would I need any monitoring?
- Which symptoms or readings mean I should stop?
- What other approaches would suit my goals?
Mention previous experiences with skipped meals, dizziness, overeating or anxiety around food.
If your work involves driving, operating equipment or physically demanding duties, describe that too. Your clinician needs to understand the day in which the proposed eating pattern would operate.
Frequently Asked Questions
Can Someone Over 60 Try Intermittent Fasting?
There is no universal answer based on age alone. Frailty, nutritional needs, health conditions and medication must be considered. Frail older adults are among the groups JAMA advises against fasting.
Should I Fast If I Take Medicine With Food?
Ask your pharmacist or prescriber before changing meal timing. Follow the medicine’s instructions until you receive individual advice.
Can I Start With a Short Fast If I Have an Eating-Disorder History?
Do not use a shorter interval to bypass the concern. Speak with your treatment team before introducing deliberate food restriction.
What If My Doctor Advises Against Fasting?
Ask about other ways to work toward your goal. You can discuss regular meal planning, nutritional support and other suitable options without adopting a fasting schedule.
Should I Continue If I Feel Faint?
Stop fasting and seek prompt medical advice. Fainting should not be treated as an expected milestone or a sign of successful fasting.
Decide About Suitability Before Timing
The first decision is whether deliberate fasting belongs in your routine at all.
If you fall into a group advised to avoid it, do not look for a more restrictive or differently branded version. If you need a medical assessment, get that assessment before changing meals or medication.
For readers who have established that fasting is appropriate, the next step is understanding the choices. Our beginner’s guide to intermittent fasting provides a starting point, while the side-effects guide explains concerns to keep in view.