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 Thyroid Supplements For Weight Loss — What You Need To Know
If you're looking for thyroid supplements to help with weight loss, it's important to understand that thyroid health and weight management are closely linked. While certain supplements may support thyroid function, sustainable weight loss in the UK typically requires a combined approach—including lifestyle changes and, in some cases, prescription weight loss medication. This guide explores what the evidence shows about thyroid supplements, when thyroid dysfunction might be affecting your weight, and how to get proper support from your GP.
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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.
Understanding Thyroid Function And Weight
The thyroid is a gland that produces hormones controlling your metabolism—the rate at which your body burns calories. When thyroid function is normal, weight management becomes primarily about calorie balance and lifestyle. However, conditions like hypothyroidism (underactive thyroid) can slow metabolism and make weight management harder, even with a reduced-calorie diet.
Common thyroid supplements marketed for weight loss include:
- Selenium — supports thyroid hormone production
- Zinc — essential for thyroid hormone metabolism
- Iodine — required for thyroid hormone synthesis
- Iron — supports thyroid function
- L-tyrosine — amino acid used in thyroid hormones
However, if you have a diagnosed thyroid condition, NHS guidance recommends prescription thyroid replacement therapy (levothyroxine) rather than supplements alone. Supplements may help only if you have a documented deficiency. Always discuss supplements with your GP before starting, as some can interfere with thyroid medications or other treatments.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Weight Loss Solutions Beyond Supplements
If you have been diagnosed with hypothyroidism and are struggling with weight management even after your thyroid medication is optimised, prescription weight loss medication may be appropriate. The NHS offers weight loss support through specialist services, including access to GLP-1 weight loss injections like Wegovy (semaglutide) for eligible adults.
Our GLP-1 weight loss calculator can help you explore potential weight loss outcomes with prescription medication. For general weight management in the UK, the NHS recommends losing weight at a steady rate of 0.5–1 kg per week through a reduced-calorie diet and increased physical activity. Use our BMI calculator to check your current BMI and understand your weight health context, then speak with your GP about the best approach for your individual situation.
- 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.
Will thyroid supplements help me lose weight?
Thyroid supplements may help only if you have a documented thyroid nutrient deficiency (selenium, zinc, or iodine). If your thyroid is functioning normally, supplements are unlikely to support weight loss. If you have hypothyroidism, prescription levothyroxine is the NHS-recommended first-line treatment, not supplements. Speak to your GP about whether supplements are appropriate for you.
Can I take thyroid supplements alongside weight loss medication like Wegovy?
Some supplements can interfere with medication absorption. Wegovy (semaglutide) is a prescription-only weight loss injection that may slow gastric emptying, which could affect how your body absorbs oral supplements or medications. Always inform your prescriber of all supplements before starting Wegovy or any weight loss medication, and space doses appropriately.
What should I do if I think my thyroid is affecting my weight?
Ask your GP for a thyroid function test (TSH and free T4). If you have hypothyroidism, your GP will prescribe levothyroxine. Once your thyroid is optimised, your metabolism should improve. If weight loss remains difficult, discuss prescription weight loss options—you may be eligible for NHS specialist services or private weight loss medication depending on your BMI and health status.
Are there foods or supplements that boost thyroid function?
Iodine-rich foods (fish, seaweed, eggs) support thyroid health, as does adequate selenium (Brazil nuts, fish) and zinc (meat, legumes). However, balanced nutrition is more important than specific supplements. If you eat a varied UK diet, you're likely getting sufficient iodine and minerals. Consult your GP or a dietitian before supplementing, especially if you have thyroid disease.
How does thyroid health relate to BMI and weight management?
Thyroid hormones regulate metabolic rate, so thyroid dysfunction can affect how many calories you burn at rest. This makes BMI changes and weight loss harder with hypothyroidism. Use our BMI calculator to track your weight health, but remember that BMI doesn't account for metabolic differences. Your GP can help adjust thyroid medication to optimise your metabolism alongside any weight loss plan.
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.