High-Strength Vitamin Supplements: Understanding the Hidden Dangers

Are your daily vitamin supplements actually helping or harming your health?

A recent investigation has raised serious concerns about how strong some vitamin supplements are becoming. Some products contain dangerously high doses of essential vitamins and minerals - far more than experts recommend. For anyone taking vitamins, this is important information to understand.

The Problem: Vitamins That Are Too Strong

In October 2025, consumer magazine Which? looked into vitamin and mineral supplements being sold on major online shopping websites. What they found was alarming: some supplements contain 12.5 times more than the safe recommended amount of popular vitamins. Imagine taking 12 tablets’ worth of vitamins in just one! Many people are unknowingly putting their health at risk because they don’t realise how strong the supplements they’re buying actually are.

Vitamin D: Too Much Can Hurt You

Vitamin D is one of the most popular supplements, especially during winter months when we don’t get enough sunlight. It’s important for strong bones and a healthy immune system.

• NHS guidance: Adults need 10 µg per day, with a maximum safe amount of 100 µg.
• Risk found: Which? identified vitamin D₃ supplements with 1,250 µg per dose — that’s 12.5× the daily recommendation.

Taking too much vitamin D can cause calcium to build up in your blood, leading to sickness, confusion, weak bones, and even kidney damage.

Vitamin A: Problems for Your Bones

Vitamin A keeps your eyes healthy, supports your skin, and boosts your immune system. You can get it from cheese, eggs, fish, milk, and liver.

• NHS guidance: Do not take more than 1,500 µg per day.
• Risk found: Which? found online shops selling 7,500 µg doses — 5× the safe amount.

Long-term high intake can weaken bones and increase fracture risk, especially with age. If you’re pregnant, too much vitamin A can harm your baby’s development.

Vitamin B6: A Risk to Your Nerves

Vitamin B6 helps your body use protein and carbohydrates and supports red blood cell formation and a healthy nervous system.

• NHS guidance: 1.4 mg/day for men and 1.2 mg/day for women.
• Risk found: Very strong tablets of 100 mg are being sold online; intakes over 200 mg can lead to peripheral neuropathy (numbness/tingling in arms and legs), affecting balance and daily tasks.

Why Are These Super-Strong Supplements Being Sold?

1. Different regulation to medicines: Supplements aren’t pre-approved like pharmaceuticals; action often happens only after harm is reported.
2. Marketing high doses: Some brands push “powerful” formulas to justify higher prices, even though more isn’t always better.
3. Online marketplace gaps: International and third-party sellers may bypass robust checks, letting unsafe products slip through.

How to Take Vitamins Safely

Dr Claire Agathou, GP at The Wellington Hospital, explains that supplements are useful when you’re not getting enough nutrients from food. However, they’re not a replacement for a healthy, balanced diet rich in whole foods.

• Check the label: Compare the dose to NHS recommendations. If it looks high, ask a doctor or pharmacist.
• Buy from trusted shops: Choose regulated retailers, pharmacies, or well-known stores.
• Look for quality marks: Independent testing seals (e.g., USP, NSF International, ConsumerLab) indicate quality checks.
• Speak to a professional: If you have health conditions, take medicines, or are pregnant/breastfeeding, get advice first.

The Bottom Line

Very strong supplements are too easy to buy online, and many people don’t realise the dangers. Used correctly, supplements can help — but too much can cause serious harm.

For manufacturers: Put safety first, label honestly, and set safe doses.
For consumers: Remember that more isn’t better. Buy from trusted sources, check doses, and seek professional advice if unsure.

References

1. ITV News (2025) ‘Why high-strength vitamin and mineral supplements can be dangerous – and what is a safe dose?’, 24 October. Available here. (Accessed: 31 October 2025).
2. NHS (2025) ‘Vitamins and minerals’. Available here. (Accessed: 31 October 2025).
3. Which? (2025) ‘Vitamin supplement warning issued for Amazon, Holland & Barrett and Superdrug’. Available here. (Accessed: 31 October 2025).