Symptoms That Indicate You Need To Stop Fasting + How To Fast Properly

Know how to listen to your body before you make any drastic dietary changes.

Medically reviewed by Madhu Sharma, RD
Written by Shaheen Naser, MSc
Edited by Arshiya Syeda, BA (Literature & Psychology), PG Dip
Fact-checked by Dipti Sharma, MA (English)  • 

Fasting is a method that most people practice for quick and effective results. While fasting comes with its set of benefits, it’s certainly not for everybody. If you show signs of exhaustion, discomfort, irritability and sickness, this is definitely your body giving you signs to stop fasting. In this article, we take you through how to fast safely and a few signs that suggest that you need to stop fasting.

Symptoms That Indicate You Should Stop Fasting

Every individual looking forward to losing weight intends to fast until they shed those excess pounds. But not all can go through the fasting phase smoothly. If you are on a fasting spree and notice any of the following symptoms, you need to stop fasting:

  • Dizziness and blurred vision
  • Loss of consciousness
  • Nausea, vomiting, and acid reflux
  • Diarrhea and indigestion
  • A burning sensation in the stomach
  • Chest pain or stomach pain
  • Menstrual irregularities
  • Difficulty concentrating, confusion, and disorientation
  • Intense headaches
  • Dry mouth and bad breath
protip_icon Quick Tip
Keeping your fasting periods short is important because more extended periods may lead to fainting, dehydration, and dizziness.

These symptoms can also shed light on some of the side effects associated with fasting. We discuss them at length in the section below.

Major Side Effects Of Fasting

The following are the major side effects associated with fasting (1):

1. May Cause Hypoglycemia

Fasting increases the risk of low blood sugar, especially for those using insulin or sulfonylureas to manage diabetes. Pregnant, lactating women, young children, older adults, and individuals with specific conditions should avoid fasting.

2. May Lead To Nutritional Deficiencies

Long-term fasting may lead to protein and nutrient deficiencies. While this can be dealt with by the intake of supplements, prolonged fasting may lead to malnourishment and several other health issues in the long run if the deficiency is undiagnosed.

3. May Cause Heart Issues

Fasting often results in insufficient energy intake and dehydration, which may affect your cardiovascular system. If you have a chronic underlying condition, like diabetes, fasting may increase your risk of coronary artery disease, stroke, asthma, and kidney issues.

Anecdotal evidence also suggests that fasting incorrectly may cause several problems like malnutrition, hair loss, skin problems, weakened immune system, fertility problems, bone loss, stroke, mood swings, muscle cramps, heart palpitations, and low blood sugar. The following tips will help you ensure you fast safely.

How To Fast Safely

1. Stay Hydrated

Image: Shutterstock

Individuals on a fast are likely to feel dehydrated. About 20 to 30% of the body’s fluid requirements are met through food, and fasting can alter this (2). Dehydration can also cause kidney damage. Hence, it is important that you prevent thirst, drink lots of water, and stay hydrated while fasting.

2. Restrict Your Calorie Intake

Image: Shutterstock

Fasting usually involves staying away from all foods/drinks for a period. However, instead of eliminating all sources of food, you can reduce your calorie intake on the days of fasting. This way, you will only consume 25% of your daily calorie requirements for two days a week to facilitate weight loss (3).

protip_icon Did You Know?
There are different types of fasting, like intermittent fasting, water fasting, juice fasting, calorie restriction, and partial fasting.

3. Do Not Feast While Breaking The Fast

As tempting as it may be to feast on all your favorite savories while breaking your fast, you should not do so. Feasting on a lot of food can cause weakness and bloating. It can also slow down the weight loss process as it will reduce the calorie deficit (4).

4. Keep The Exercises Mild

Image: Shutterstock

When you are on a diet, your body runs low on energy. Hence, keep your exercises mild. Indulge in strenuous workouts only on the days you aren’t fasting. As your body gets used to exercising, you can gradually start trying out high-intensity workouts to increase the utilization of the stored fat in your body (5).

5. Take Additional Supplements

Image: Shutterstock

When you fast, you tend to miss out on a lot of nutrients essential for your body. People on a diet are deficient in a number of nutrients – including calcium, iron, and vitamin B12 (6). You can make up for these deficiencies by taking a nutritional supplement after consulting your healthcare provider.

6. Eat Whole Foods During Non-Fasting Days

Image: Shutterstock

It is important you eat whole foods on non-fasting days. This not only prevents deficiencies and hunger pangs but also cuts the risk of severe illnesses like heart disease and cancer (7).

7. Eat More Protein

Image: Shutterstock

Consuming more protein is a necessity not only while working out but also when you want to lose fat and build muscles. Increase your intake of protein-rich foods like chicken, eggs, cheese, fatty fish, and nuts during the period you are not fasting (8).

Infographic: What To Eat To Break Your Fast?

Fasting is a popular practice with many health benefits. However, you should first know everything about this practice — what to eat during a fast and how to break it. Also, not all foods are ideal while breaking your fast. Check out the infographic below to learn about the foods you can consume when you break a fast.

what to eat to break your fast (infographic)

Illustration: StyleCraze Design Team

Save the high-quality PDF version on your device now.

Download Infographic in PDF version Download Infographic
Download Infographic in PDF version

While fasting once in a while can help cleanse and detox your system, you should not overdo it. Dizziness, nausea, vomiting, chest pain, or irregular menstruation are all signs to stop fasting. Staying well hydrated, with ample supplements, mild exercise, and restricted calorie intake can help you fast in a healthy and more effective way.

Frequently Asked Questions

Can fasting cause diabetes and damage the pancreas?

Jesse Feder, Clinical Dietitian at the Memorial Regional Hospital, says, “While fasting will not directly cause diabetes, there is limited evidence showing that it may damage pancreatic cells and inhibit proper insulin production. This can contribute to the development of diabetes. However, it is also important to note there is also evidence showing that fasting can help the pancreas regenerate healthy cells and improve insulin production. At the moment, this topic needs further investigation.”

Can fasting cause Insomnia?

Jesse says, “Insomnia or trouble sleeping is one of the most common side effects when you begin fasting. However, after about 1–2 weeks, your sleep will improve. As far as the science goes, fasting typically reduces your insulin levels while increasing melatonin. This can help make you feel calm and sleepy before bed.”
He adds, “Orexin-A, a neurotransmitter linked to alertness, has been shown to be reduced at night in those who fast and increased during the day. It is important to note that prolonged fasting may lead to an increase in the level of cortisol, the stress hormone. This may eventually make it more difficult to sleep or make you feel not well-rested. This is why I recommend only short-term or intermittent fasting if you want to go that route.”

Is it normal to throw up while water fasting?

Throwing up or vomiting is one of the many indicators that you need to give fasting a break for some time. Hence, if you throw up on a water fast, it is best to start eating something until you are healthy enough to continue fasting.

When should I quit water fasting?

If you experience any symptoms like vomiting, nausea, dizziness, loss of consciousness, diarrhea/constipation, or abdominal pain, you should stop fasting immediately.

Can fasting make you sick?

Yes, fasting can cause dehydration, which may lead to other undesirable consequences.

Is it safe to fast for 3 days?

You can fast safely for 2-3 days without experiencing any adverse health effects (9). But, we suggest you prepare your body for water fasting by consuming fewer foods on the days prior.

What not to eat after fasting?

You should not binge on junk foods or other saturated foods after fasting. This may affect your weight loss progress by disrupting the calorie deficit you have created.

Who all should not fast?

People with diabetes, cardiac, or renal problems or on medicines for any medical conditions should avoid fasting. Pregnant and lactating women should also avoid fasting.

How long does your body take to start burning stored fat while fasting?

Factors like body weight and the type of fasting affect how long it takes to burn body fat. But, in general, your body is estimated to start burning body fat after 12 to 48 hours of fasting.

What is considered long-term fasting?

Fasting from 5 to 21 days is considered long-term. Do ensure to consult your doctor before you take up fasting. They can give you further information based on your body type and current health status.

Why do legs hurt when fasting?

Lack of adequate nutrient intake and low consumption of water during fasting can lead to electrolyte imbalance and dehydration. This results in sore muscles and pain in the legs.

Key Takeaways

  • Fasting is a common method for quickly losing weight. Rapid weight loss can sometimes cause dizziness, nausea, and fatigue.
  • The key to proper fasting is staying hydrated. A diet rich in protein and whole foods also ensure that your blood sugar level doesn’t drop and keeps you from fainting.
  • When on diet, it is recommended to keep the exercises mild and take additional supplements to avoid nutritional deficiencies and decreased immunity.

Is fasting not good for your health? Watch the video below to know more about when to stop fasting and why it is dangerous to continue.


Articles on StyleCraze are backed by verified information from peer-reviewed and academic research papers, reputed organizations, research institutions, and medical associations to ensure accuracy and relevance. Read our editorial policy to learn more.

  1. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus, National Library Of Medicine
  2. Contribution of Water from Food and Fluids to Total Water Intake: Analysis of a French and UK Population Surveys” Nutrients, US National Library Of Medicine, National Institutes of Health.
  3. Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults.” American Journal Of Clinical Nutrition, US National Library Of Medicine, National Institutes of Health.
  4. Diet in the management of weight loss” Canadian Medical Association Journal, US National Library Of Medicine, National Institutes of Health.
  5. Metabolic responses to exercise after fasting.” Journal of Applied Physiology, US National Library Of Medicine, National Institutes of Health.
  6. Prevalence of micronutrient deficiency in popular diet plans” Journal Of The International Society of Sports Nutrition, US National Library Of Medicine, National Institutes of Health.
  7. Mediterranean Diet and Prevention of Chronic Diseases” Nutrition Today, US National Library Of Medicine, National Institutes of Health.
  8. Preserving Healthy Muscle during Weight Loss” Advances in Nutrition, US National Library Of Medicine, National Institutes of Health.
  9. Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting” BMC Complementary and Alternative Medicine, US National Library Of Medicine, National Institutes of Health.
Was this article helpful?
The following two tabs change content below.

Latest Articles