Balancing weight loss medications like Mounjaro and Wegovy while fasting has become a common concern for a lot of patients. GLP-1 medications have transformed weight management for thousands of people in the UK, but they also raise questions about how they might affect fasting.
Fasting means different things to different people – from religious practices to intermittent fasting for weight loss. And when you’re taking medication that affects your appetite and blood sugar, fasting requires careful consideration.
Traditional fasting typically involves avoiding all food and sometimes even water throughout the day. This might be for a short or 24-hour fast, often practised for religious or spiritual purposes.
Intermittent fasting is a more structured approach that alternates between eating and fasting periods. Popular methods are:
While traditional fasting often focuses on spiritual benefits, intermittent fasting is primarily for potential health benefits like improved insulin sensitivity and weight management.
People fast for various reasons, and their different motivations shape how someone might approach fasting while taking medications.
Religious fasting is among the oldest and most common reasons people temporarily abstain from food.
These religious fasts are meaningful spiritual practices that often can’t be modified or skipped and often follow specific patterns and rules:
People fast for health reasons that range from everyday wellness to specific medical needs. Common health-related fasting includes:
Many people turn to fasting as a straightforward approach to weight management. Unlike complicated diet plans with long lists of allowed and forbidden foods, fasting restricts when you eat, not what you eat.
Weight loss through fasting typically happens because it naturally reduces your total calorie intake. When you have fewer hours to eat during the day, you generally consume fewer calories overall. For many people, this approach feels less restrictive than traditional diets.
Beyond just weight loss, some people report that fasting helps reset their relationship with food, decreases mindless snacking, and increases awareness of true hunger versus emotional eating.
Weight loss medications like Mounjaro (tirzepatide) and Wegovy (semaglutide) work by slowing digestion, increasing feelings of fullness and helping regulate blood sugar levels.
Some studies have even found that when patients combine intermittent fasting with their GLP-1 medications, they often see better weight loss results than using just the medication or fasting alone.
Taking Wegovy or Mounjaro whilst fasting is generally safe, but timing matters. These medications already slow digestion and reduce appetite, making fasting easier for some people but more challenging for others.
Most doctors recommend taking weight loss medication on the same day and time each week, regardless of your fasting schedule. Consistency will help maintain steady levels of the medication in your system. If your injection day falls during a fast, you can still take the medication as scheduled.
If you’re fasting for diet reasons, start with shorter fasting windows (12-16 hours). This allows you to see how your body responds before attempting longer fasting periods. Many people find that the appetite-suppressing effects of these medications actually make fasting more comfortable than it would be otherwise.
If you’re fasting for religious reasons, try injecting about 30 minutes before breaking your fast to help manage hunger when you do eat and prevent overeating after fasting. The appetite-suppressing effects can be particularly helpful during religious fasting, like Ramadan. You’re also exempt from fasting during Ramadan if you have a chronic illness and take daily medication for it, like high blood pressure, high cholesterol or epilepsy.
For safety, be aware of potential side effects and low blood sugar symptoms like dizziness, irritability, shakiness, or confusion. These risks increase when combining fasting with GLP-1 medications, especially for people who also take diabetes medications.
While fasting, exercise requires extra care when taking medication, as it already affects energy levels and how the body processes fuel.
Lighter activities like walking, gentle yoga, or stretching are better while you’re fasting. These low-intensity exercises use primarily fat for fuel and are less likely to cause blood sugar drops when combined with GLP-1 medications.
For more intense workouts like running, weightlifting, or high-intensity interval training, try to schedule them closer to your meals or your eating windows. This gives your body the necessary fuel and helps prevent dizziness or weakness during exercise.
Stay alert to how your body feels during activity. Symptoms like unusual fatigue, dizziness, or heart palpitations while exercising in a fasted state may signal that you need to adjust your approach.
Staying properly hydrated is essential when combining fasting with medications like Mounjaro and Wegovy.
For religious fasts that restrict water (like during Ramadan), focus on hydrating well during permitted times. Add electrolytes to your water before and after fasting, especially if you experience headaches or fatigue.
Be aware that Mounjaro and Wegovy can cause dehydration through side effects like nausea, vomiting, or diarrhoea. These risks increase when you’re not eating regularly. If you notice dark urine, dizziness when standing, or severe headaches, these could be signs of dehydration needing immediate attention.
The foods you choose to eat when taking Wegovy and Mounjaro become especially important when you’re combining fasting and taking medication. These medications already affect how your body processes nutrients, so your food choices can help maximise benefits and minimise side effects.
When you can eat, focus on protein-rich foods like lean meats, fish, eggs, and legumes.
Protein helps preserve muscle mass during weight loss and provides lasting fullness, which works with your medication’s appetite-suppressing effects.
Include plenty of fibre from vegetables, fruits, and whole grains. Both fasting and GLP-1 medications can slow digestion, so eating enough fibre helps maintain regularity and gut health.
Healthy fats from sources like avocados, nuts, and olive oil will give you essential nutrients and help you feel satisfied with smaller portions. These foods are calorie-dense but nutritious, making them valuable when your eating windows are limited.
Avoid breaking your fast with large, heavy meals, which can cause increased digestive discomfort when combined with these medications. Instead, start with smaller portions and eat slowly to let your body adjust.
If you’re fasting while taking Mounjaro or Wegovy, pay close attention to how your body responds. These medications work differently for everyone, and combining them with fasting requires some extra care.
Keep your doctor or pharmacist informed about your fasting practices, especially if you notice any concerning symptoms. Timing your medication, staying well-hydrated during non-fasting periods, and choosing nutrient-dense foods when you eat will help support your body through fasting and medication effects.
If you’re a Click2Pharmacy patient using weight loss medications, our pharmacy team is available by email to answer any questions about managing your treatment while fasting.
You can take Wegovy (semaglutide) while fasting, and most healthcare providers recommend maintaining your regular weekly schedule, even during fasting periods. If you’re concerned about potential side effects like nausea or low blood sugar during fasting, time your injection shortly before breaking your fast.
From a medical perspective, Mounjaro (tirzepatide) injections don’t break a fast since they don’t contain calories or trigger digestive processes in the same way food does. The medication is delivered via a small injection under the skin, not through the digestive system.
For intermittent fasting focused on metabolic benefits, taking Mounjaro won’t interfere with these goals. However, if you’re fasting for religious reasons, you should consult with your religious advisor about whether medications are permitted during your specific fasting practice.
Weight loss tablets have different requirements than injectable GLP-1 medications. Many oral weight loss medications must be taken with food to work properly or minimise side effects. For example, Orlistat (Xenical, Alli) works by blocking fat absorption from meals containing fat to be effective.
If you’re using oral weight loss medications, talk to your healthcare provider about potentially adjusting your dosing schedule around your fasting periods. Never stop or change your medication schedule without professional guidance.
