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 Supplements To Take While On Mounjaro
If you're taking Mounjaro (tirzepatide), you may be wondering which supplements are safe and beneficial to add to your routine. Because Mounjaro slows how quickly food leaves your stomach and affects nutrient absorption, choosing the right supplements becomes important for supporting your health whilst on this prescription weight management injection. Always discuss any new supplements with your GP or prescriber before starting, as some may interact with Mounjaro or reduce its effectiveness.
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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.
Key Supplements To Consider With Mounjaro
Several supplements may be particularly helpful whilst taking Mounjaro, especially those addressing common nutritional gaps:
- Vitamin B12: Mounjaro can reduce stomach acid, which may affect B12 absorption. A sublingual or injectable B12 supplement (methylcobalamin form) bypasses the stomach and supports energy and neurological function.
- Iron: Reduced stomach acid also impacts iron absorption. If your GP suspects iron deficiency, a ferrous supplement taken with vitamin C (not with Mounjaro) may help — women of reproductive age are at particular risk.
- Calcium and Vitamin D: Slower gastric transit may reduce calcium absorption. Vitamin D supports calcium uptake and is especially important for bone health if you're losing weight rapidly.
- Electrolytes: If you experience diarrhoea or vomiting as a side effect, an electrolyte supplement or rehydration salts can help maintain sodium, potassium, and magnesium levels.
- Digestive enzymes: Some people find gentle enzyme supplements help with bloating or indigestion, though evidence is modest. Always check with your GP first.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Supplements To Avoid Or Use Cautiously
Not all supplements are safe to combine with Mounjaro. Avoid taking oral contraceptives or other oral medications at the same time as your Mounjaro dose — Mounjaro may reduce their absorption. Space them at least 4 hours apart, or switch to a non-oral contraceptive method if you're concerned about reliability. Herbal supplements like ginger, peppermint, or psyllium husk may also slow gastric emptying further, potentially worsening nausea. Fat-soluble vitamin supplements (A, D, E, K) should be taken with food, but because Mounjaro reduces appetite and food intake, discuss with your GP whether supplementation is necessary or if dietary sources are sufficient. Always inform your prescriber of any supplements, as some may interact with underlying health conditions you're being a UK pharmacy for.
- 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.
Do I need to take supplements whilst on Mounjaro?
Not necessarily — many people maintain adequate nutrition through food alone. However, because Mounjaro affects stomach acid and nutrient absorption, your GP may recommend specific supplements based on your blood work or diet. Vitamin B12 and iron are the most commonly suggested. Have a conversation with your GP or a registered dietitian to assess your individual needs.
Can I take a multivitamin with Mounjaro?
A basic multivitamin is usually fine, but timing matters. Take it with a meal, not with your Mounjaro injection. Avoid multivitamins very high in iron or calcium unless advised by your GP, as these may not absorb well. Some people find breaking a multivitamin into smaller doses throughout the day helps absorption better than one large dose.
Should I take supplements on the same day as my Mounjaro injection?
Yes, it's generally safe to take most supplements on injection day, but space them out. Take your Mounjaro injection, then wait at least 30 minutes before taking other oral supplements or medications. This minimises any potential interaction with absorption. Your prescriber can give personalised guidance based on your specific supplements.
What if I feel weak or tired on Mounjaro — which supplements help?
Fatigue can indicate B12 or iron deficiency. Before taking supplements, ask your GP for a blood test (full blood count and B12 level) to check. If deficient, a B12 sublingual spray or iron supplement taken with vitamin C can help. Dehydration also causes fatigue — drink adequate water, especially if you have nausea or diarrhoea.
Can supplements help with Mounjaro side effects like nausea?
Ginger supplements are often suggested for nausea, but they may slow stomach emptying further, potentially worsening the problem. Instead, focus on eating small, frequent meals and staying hydrated. If nausea is severe or persistent, speak to your GP — it may indicate a need for dose adjustment. Never self-treat with supplements without professional guidance.
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.