Jump to: When you actually need supplements | The supplement industry reality | Food vs pills comparison | Evidence-based guidance | Take home message
Most people taking Mounjaro don’t need vitamin supplements. While the supplement industry wants you to believe otherwise, a diet based on whole foods with enough variety provides everything your body needs.
The supplement industry is largely unregulated, with inconsistent dosing and quality control. Many multivitamins contain nutrients that compete with each other for absorption, meaning you’re paying for vitamins you can’t actually use.
More importantly, relying on supplements can create what’s called a ‘pill mentality’, the belief that taking vitamins can ‘make up for’ unhealthy eating habits.
However, there are generally only 4 specific situations where targeted vitamins make sense while taking Mounjaro:
- Following a plant-based diet,
- during UK winter months,
- losing weight too quickly (although, we wouldn’t recommend a supplement in this scenario, but rather slowing down the rate of weight loss),
- or treating a diagnosed deficiency.
Understanding when supplements are actually necessary – versus when the industry wants you to think they are – helps you make informed decisions about your health and how to approach weight loss on Mounjaro.
When you actually need supplements
Despite what supplement companies suggest, only specific circumstances require vitamins while taking Mounjaro.
Genuine supplement needs:
Plant-based diets: Vitamin B12 isn’t naturally available in plant foods, making supplementation essential for vegans and some vegetarians. This isn’t optional; it’s a medical necessity.
UK winter months: Our bodies can’t produce vitamin D without adequate sunlight. From October through March, most UK residents benefit from vitamin D3 supplementation.
Rapid weight loss: Losing more than 1kg weekly can compromise nutrient intake. However, the solution isn’t supplements; it’s eating more protein and increasing portion sizes to slow your weight loss.
Diagnosed deficiencies: If blood tests show deficiencies, follow your GP’s specific recommendations for treating the deficiency.
What doesn’t require supplements:
Taking Mounjaro itself doesn’t create vitamin deficiencies. The medication works by reducing appetite, not by blocking nutrient absorption.
Feeling tired or having low energy while losing weight is normal and rarely solved by vitamins. Better sleep and adequate nutrition work far more effectively.
Most people worry about ‘missing nutrients’ when eating less, but eating nutrient-dense foods easily meets daily requirements.
The supplement industry reality
The vitamin industry operates with minimal regulation, creating several problems that affect your health.
Quality control issues
Independent testing consistently finds that supplement labels don’t match actual contents. For example, one study found that 83% of 30 products tested had inaccurate labels and 7 of the 30 products contained hidden components not listed on the label.
Unlike prescription medications, supplements don’t require proof they work before reaching shop shelves. Companies can make vague health claims without demonstrating actual benefits.
Nutrient competition problems
High-dose multivitamins often contain nutrients that block each other’s absorption. Taking large amounts of zinc interferes with copper absorption, while calcium blocks iron uptake.
Your body absorbs nutrients from food more efficiently than from isolated supplements. The vitamin C in an orange works differently than vitamin C powder because food provides complementary compounds that enhance absorption.
The ‘pill mentality’ trap
Supplement marketing encourages the belief that pills can compensate for poor dietary choices. This creates a dangerous mindset where people prioritise supplements over fundamental nutrition improvements.
Research suggests that people who take multivitamins often have worse diets than those who don’t, possibly because they believe supplements provide nutritional insurance.
Taking vitamins feels like ‘doing something healthy’ while requiring no behaviour change. Real health improvements come from eating better foods, not from adding pills to poor eating habits.
Food vs pills: cost and effectiveness comparison
Whole foods provide superior nutrition at lower costs than supplements, with better absorption and additional health benefits.
| Nutrient |
Monthly supplement cost |
Food alternative |
Monthly food cost |
Additional benefits |
| Vitamin C (90mg daily) |
£8-15 |
1 orange daily |
£6-8 |
Fibre, folate, potassium, natural sugars |
| Iron (18mg daily) |
£12-20 |
150g lean beef twice weekly |
£16-20 |
High-quality protein, B12, zinc |
| Vitamin D (25mcg daily) |
£8-12 |
2 portions oily fish weekly |
£8-12 |
Omega-3s, protein, selenium |
| Calcium (1000mg daily) |
£10-18 |
200ml milk + 30g cheese daily |
£12-15 |
Protein, B12, phosphorus |
| B Vitamins (complex) |
£15-25 |
Varied whole grains, eggs, meat |
£20-25 |
Protein, fibre, healthy fats |
| Multivitamin |
£25-40 |
Balanced whole food diet |
£50-80 (per person) |
Hundreds of beneficial compounds |
Why food wins
Better absorption: Your body recognises nutrients in food more easily than isolated vitamins. The iron in spinach comes with vitamin C that enhances absorption naturally.
Synergistic effects: Foods contain hundreds of compounds that work together. An apple provides vitamin C alongside quercetin and fibre that supplements can’t replicate.
Satiety and satisfaction: Eating nutrient-rich foods helps you feel full and satisfied. Taking vitamins while eating poor-quality food leaves you hungry and undernourished.
No competition issues: Nutrients in food rarely interfere with each other because they’re present in appropriate ratios that your body expects.
Real-world example
Instead of spending £35 monthly on a premium multivitamin, invest that money in:
- Extra portions of vegetables (£8-10)
- Higher-quality protein sources (£10-12)
- Seasonal fruits (£6-8)
- Nuts, seeds, or whole grains (£8-10)
You’ll get superior nutrition, feel more satisfied, and develop sustainable eating habits that support long-term health.
Evidence-based guidance for genuine needs
When supplements are genuinely necessary, follow evidence-based dosing and timing recommendations.
Vitamin B12 (for plant-based diets)
- Dose: 2.4mcg daily, or 250mcg weekly
- Form: Cyanocobalamin (most stable and researched)
- Timing: With breakfast for best absorption
- Cost: £6-10 monthly
Vitamin D3 (October-March in UK)
- Dose: 25mcg (1,000 IU) daily
- Timing: With a meal containing fat
- Duration: October through March
- Cost: £5-8 monthly
Iron (or other diagnosed deficiencies)
- Dose: As prescribed by GP (usually 65-200mg elemental iron)
- Timing: Away from calcium, coffee, and tea
- Enhancement: Take with vitamin C
- Monitoring: Blood tests every 3 months
What to avoid
Megadoses: More isn’t better with vitamins. High doses can interfere with absorption of other nutrients and cause side effects.
Unnecessary combinations: Most multivitamins provide nutrients you don’t need while skimping on ones you might actually require.
Expensive formulations: ‘Chelated’ minerals and ‘pharmaceutical grade’ vitamins rarely justify their premium pricing. Basic forms work just as well.
Timing mistakes
Don’t take supplements on an empty stomach unless specifically recommended. Most vitamins absorb better with food.
Avoid taking multiple supplements simultaneously. Space them throughout the day when possible.
Never assume supplements replace the need for medical monitoring if you have health conditions.
Monitoring your approach
Signs you don’t need supplements:
You’re eating a varied diet with plenty of vegetables, fruits, proteins, and whole grains. Your energy levels are stable, and you’re not experiencing unexplained symptoms.
Blood test results show normal vitamin and mineral levels. You’re losing weight at a sustainable pace (0.5-1kg weekly) while feeling satisfied with your meals.
Signs to reconsider:
You’re restricting entire food groups unnecessarily. You’re losing weight very rapidly and feeling weak or fatigued beyond normal adjustment periods.
Blood tests reveal deficiencies despite eating well. You’re following a medically necessary restricted diet that limits certain nutrients.
Getting proper assessment:
If you’re concerned about nutrient status, request blood tests from your GP rather than guessing. Focus on vitamin D, B12, iron studies, and a full blood count.
Avoid expensive ‘nutritional assessments’ from supplement companies or health food shops. These often use unreliable testing methods designed to sell products.
Take home message
The supplement industry profits from making healthy people worry about imaginary deficiencies. Most people taking Mounjaro get everything they need from food.
Focus your time and money on improving your diet rather than relying on supplements to make up for unhealthy eating habits.
An extra portion of vegetables, higher-quality protein, or seasonal fruit provides far more benefit than expensive multivitamins.
If you genuinely need supplements – B12 for plant-based diets, vitamin D during winter, or treating diagnosed deficiencies – choose basic, independently tested products rather than expensive formulations with marketing big claims.
Remember that sustainable weight loss comes from developing healthy eating habits, not from taking pills. Supplements can’t teach you how to enjoy vegetables, cook balanced meals, or finding alternative coping strategies to manage challenging emotions.
Second Nature's Mounjaro programme
Second Nature provides Mounjaro as part of our Mounjaro weight-loss programme
Why choose Second Nature over other medication providers, assuming you’re eligible?
Because peace of mind matters.
We’ve had the privilege of working with the NHS for over eight years, helping people across the UK take meaningful steps toward a healthier, happier life.
Our programmes are designed to meet people where they are, whether that means support with weight loss through compassionate one-to-one health coaching, or access to the latest weight-loss medications (like Mounjaro) delivered alongside expert care from a multidisciplinary team of doctors, psychologists, dietitians, and personal trainers.
At the heart of everything we do is a simple belief: real, lasting change comes from building better habits, not relying on quick fixes. We’re here to support that change every step of the way.
With over a decade of experience, thousands of lives changed, and a long-standing record of delivering programmes used by the NHS, we believe we're the UK’s most trusted weight-loss programme.
We hope to offer you something invaluable: peace of mind, and the support you need to take that first step.
