The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Best Electrolytes on Mounjaro: What You Need to Know
When taking Mounjaro (tirzepatide), nausea and dehydration are common side effects that can affect your electrolyte balance. Unlike Wegovy, which is a GLP-1 only medication, Mounjaro works as a dual GIP and GLP-1 receptor agonist, which may cause stronger initial gastrointestinal effects. Maintaining proper electrolyte levels is important for your health during weight management treatment. This guide covers practical strategies for staying hydrated and maintaining electrolytes while on Mounjaro, alongside your reduced-calorie diet and increased physical activity.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Why Electrolytes Matter on GLP-1 Medications Like Mounjaro
Electrolytes (sodium, potassium, magnesium, and calcium) are minerals that regulate nerve signals, muscle function, and fluid balance in your body. When you take Mounjaro during dose titration, especially in the early weeks, nausea and vomiting are very common side effects. This causes fluid loss, which can disrupt electrolyte levels and lead to fatigue, muscle weakness, or dizziness.
Dehydration is particularly common on GLP-1 medications because they slow gastric emptying and reduce appetite, meaning you may drink less without realising it. The combination of reduced food intake and fluid loss from nausea creates a double effect on electrolyte balance. Your prescriber will assess your suitability for Mounjaro during a clinical assessment, and it's important to flag any existing kidney or heart conditions that affect electrolyte handling. Unlike Wegovy, Mounjaro's dual mechanism may cause more pronounced gastrointestinal symptoms in some people, making hydration even more critical.
- Electrolytes regulate muscle and nerve function
- Nausea and vomiting deplete fluids and minerals
- Reduced food intake means fewer electrolytes from diet
- Dehydration is a common but manageable side effect
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
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Practical Electrolyte Management While on Mounjaro
The best approach is prevention through consistent hydration and balanced eating. Drink at least 2–3 litres of water daily, even if you're not thirsty—thirst is a late sign of dehydration. Include electrolyte-rich foods in small, frequent meals: bananas (potassium), leafy greens (magnesium), and low-sodium broths (sodium). If nausea is severe during your Mounjaro UK prescription dose titration, consider sugar-free electrolyte drinks like coconut water or over-the-counter oral rehydration solutions (ORS).
Avoid high-sugar sports drinks, which can trigger nausea further. If you experience persistent dizziness, muscle cramps, or irregular heartbeat—all signs of electrolyte imbalance—contact your GP immediately. Your prescriber can advise whether electrolyte supplementation is needed. Try our free BMI calculator and GLP-1 weight loss calculator to track your health metrics alongside your Mounjaro progress.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Should I take electrolyte supplements while on Mounjaro?
Most people maintain electrolytes through diet and water alone. Only consider supplements if your GP recommends them or you experience symptoms like severe fatigue or muscle cramps. Always discuss with your prescriber before starting any new supplements, as some may interact with Mounjaro or your other medications.
Is electrolyte loss worse on Mounjaro than Wegovy?
Both GLP-1 medications can affect hydration, but Mounjaro's dual GIP and GLP-1 mechanism may cause stronger initial nausea in some people. Individual experience varies widely. Your prescriber will assess which medication suits you best during your clinical assessment.
How much water should I drink on Mounjaro?
Aim for at least 2–3 litres daily, or more if you're experiencing nausea or live in a hot climate. Drink little and often rather than large amounts at once, which may trigger nausea. Listen to your body and increase intake if you feel thirsty.
What are signs of electrolyte imbalance I should watch for?
Severe fatigue, muscle cramps, dizziness, headaches, or irregular heartbeat are warning signs. Mild fatigue is common in the first few weeks, but worsening symptoms warrant a GP visit. Your prescriber can check your electrolytes if concerned.
Can electrolyte loss affect my BMI or weight loss on Mounjaro?
Electrolyte imbalance won't stop weight loss, but it can make you feel unwell and reduce your ability to exercise. Proper hydration supports metabolism and helps you feel your best during treatment. Use our free progress tracker to monitor how you feel alongside your weight changes.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.