---
title: "Vitamin D 400iu — £39K/yr Amazon UK Niche (2026) - Flapen"
canonical_url: "https://flapen.com/research/uk/health-personal-care/vitamin-d-400iu"
last_updated: "2026-07-31T16:25:20.154Z"
locale: en
meta:
description: "Niche score 27/100 · £39K/yr market · 55K searches/yr · £4.03 avg price. Doesn't clear our bar today. Data updated Jul 2026."
"og:description": "Niche score 27/100 · £39K/yr market · 55K searches/yr · £4.03 avg price. Doesn't clear our bar today. Data updated Jul 2026."
"og:title": "Vitamin D 400iu — £39K/yr Amazon UK Niche (2026) - Flapen"
---
# **vitamin d 400iu**
**Skip it**
A concentrated shelf (top 5 take 100% of clicks) — this niche doesn't clear our bar today.
Market size 10Growth 1Conversion 98Competition 0Returns 100Price range 0Avg price 11Brand share 0Review moat 47Quality gap 25
**Returns**
**Incredible****0.0%**
return rate — above 5% kills the launch gate
**Conversion**
**Incredible****17.5%**
search→purchase rate — share of searches ending in a sale
**Review moat**
**Okay****1,793.25**
avg incumbent reviews — the moat a new listing must climb
**Quality gap**
**Okay****4.6★**
avg incumbent rating — lower means beatable quality
**Avg price**
**Bad****£4.03**
avg listing price — sweet spot $15–$100
**Market size**
**Bad****£39K**
£39K/yr · 55K searches
**Growth**
**Bad****-49.0%**
90-day search growth — must beat 0% to launch
**Competition**
**Bad****100%**
top-5 click share — a locked-up shelf
**Brand share**
**Bad****100%**
top-5 brand share — brand-locked demand
**Price range**
**Bad****£2.63–£7.03**
cheapest to priciest tracked listing — scored on the share inside $15–$100
According to Flapen's Amazon United Kingdom niche tracking, vitamin d 400iu is a £39K/yr Amazon United Kingdom market (55K searches/yr). The top 5 brands hold 100% of demand. Demand peaks in Jan–Feb–Oct–Nov. Verdict: Skip it — 27/100.
Data updated Jul 25, 2026 · scored weekly · [~~How we score niches ~~](https://flapen.com/research/methodology)
## **vitamin d 400iu market data**
- **Units sold / yr**
- **10K–13K**
- avg 1,500–2,000/product
- **Revenue / yr**
- **£40K–£50K**
- units × avg price
- **Conversion rate**
- **17.5%**
- **Avg BSR**
- **#41**
- **Page quality**
- **0%**
- **Prime**
- **100%**
- **Sponsored**
- **100%**
- **Out of stock**
- **0.0%**
- **Avg brand age**
- **79 months**
- **Avg seller age**
- **174 days**
## **Competition & brand share**
The top 5 products capture 100% of clicks — a locked-up shelf that new listings rarely crack.
**Brands**
**4 **▼falling
**Sellers**
**16**
**Top-5 brand share**
**100%**
Top 20: 100%
**Top-5 click share**
**100%**
Top 20: 100%
**Open market**
**0%**
- Vitabiotics Ultra53% - Fultium23% - Natures Aid19% - PROHEALTH4% - Open — no brand owns it (0%)
## **Demand & seasonality**
Weekly Amazon search volume, last 86 weeks — -49.0% search growth over the last 90 days.
2K2KSpike '25Spike '26 seasonDecJanFebMarAprMayJunJulAugSepOctNovDecJanFebMarAprMayJun
Peak months: Jan, Feb, Oct, Nov · busiest ÷ quietest = 2.8×
[**Open Trend **](https://flapen.com/research/uk/health-personal-care/vitamin-d-400iu/trend)
## **Top vitamin d 400iu search terms**
- **vitamin d 400iu**19K/yr-54.1%17.5% conv. - **vitamin d3 400iu**8K/yr-61.2%10.9% conv. - **vitamin d 400 iu**7K/yr-36.0%20.5% conv. - **vitamin d 10 micrograms**10K/yr-60.3%12.4% conv. - **vitamin d 10mcg**5K/yr-18.1%20.1% conv. - **vitamin d 10mg**4K/yr-34.7%11.1% conv. - **vitamin d 400**3K/yr-17.2%18.7% conv. [**All search terms **](https://flapen.com/research/uk/health-personal-care/vitamin-d-400iu/search-terms)
## **Top vitamin d 400iu products on Amazon**
Each bubble is one product — market share against review moat; bubble size tracks estimated sales, color grades how beatable the incumbent looks.
0%15%£6K30%£12K45%£17K60%£23K101001K10K Reviews — right = deep review moatMarket share (90d) ≈ est. sales
Beatable (≤4.3★) Contested Strong incumbent (>4.7★)
All 4 tracked products in this niche — three views at once, no toggling.
### **Top sellers**
by 90-day click share
[1**Vitamin D Tablets 400IU Vitabiotics Ultra**Vitabiotics Ultra**£2.63**4.7★1,658 rev](https://www.amazon.co.uk/dp/B0CZ7C4JWR) [2**Fultium Vitamin D3 400 IU 10g |90 Tablets|Recommended Daily Dose Vitamin D Supplement | Immune Bone & Muscle Support | from The UKs No.1 Vitamin D Prescription Brand | Vegetarian | Food Supplement**Fultium**£2.80**4.6★58 rev](https://www.amazon.co.uk/dp/B0GH75SGB3) [3**Natures Aid Vitamin D3 10g (400IU) High Strength Vitamin D Supplement Supports Bones Muscles & Immunity Vegan Gluten-Free Non-GMO 90 Tablets Essential Daily Nutrient**Natures Aid**£3.65**4.6★5,083 rev](https://www.amazon.co.uk/dp/B002F5FODG) [4**Certified Vegan 400IU Vitamin D3 120 Days Tablets for Pregnancy Nursing and Seniors - NHS Approved**PROHEALTH**£7.03**4.5★374 rev](https://www.amazon.co.uk/dp/B09GHR7471)
### **Newest**
by launch date
[**Fultium Vitamin D3 400 IU 10g |90 Tablets|Recommended Daily Dose Vitamin D Supplement | Immune Bone & Muscle Support | from The UKs No.1 Vitamin D Prescription Brand | Vegetarian | Food Supplement**Fultium**£2.80**58 rev5mo ago](https://www.amazon.co.uk/dp/B0GH75SGB3) [**Vitamin D Tablets 400IU Vitabiotics Ultra**Vitabiotics Ultra**£2.63**1,658 rev2y ago](https://www.amazon.co.uk/dp/B0CZ7C4JWR) [**Certified Vegan 400IU Vitamin D3 120 Days Tablets for Pregnancy Nursing and Seniors - NHS Approved**PROHEALTH**£7.03**374 rev4y ago](https://www.amazon.co.uk/dp/B09GHR7471) [**Natures Aid Vitamin D3 10g (400IU) High Strength Vitamin D Supplement Supports Bones Muscles & Immunity Vegan Gluten-Free Non-GMO 90 Tablets Essential Daily Nutrient**Natures Aid**£3.65**5,083 rev17y ago](https://www.amazon.co.uk/dp/B002F5FODG)
### **Trending**
90-day click momentum
[**Fultium Vitamin D3 400 IU 10g |90 Tablets|Recommended Daily Dose Vitamin D Supplement | Immune Bone & Muscle Support | from The UKs No.1 Vitamin D Prescription Brand | Vegetarian | Food Supplement**Fultium**£2.80**4.6★**▲ 307%**](https://www.amazon.co.uk/dp/B0GH75SGB3) [**Vitamin D Tablets 400IU Vitabiotics Ultra**Vitabiotics Ultra**£2.63**4.7★**▼ 11%**](https://www.amazon.co.uk/dp/B0CZ7C4JWR) [**Natures Aid Vitamin D3 10g (400IU) High Strength Vitamin D Supplement Supports Bones Muscles & Immunity Vegan Gluten-Free Non-GMO 90 Tablets Essential Daily Nutrient**Natures Aid**£3.65**4.6★**▼ 19%**](https://www.amazon.co.uk/dp/B002F5FODG) [**Certified Vegan 400IU Vitamin D3 120 Days Tablets for Pregnancy Nursing and Seniors - NHS Approved**PROHEALTH**£7.03**4.5★**▼ 62%**](https://www.amazon.co.uk/dp/B09GHR7471)
## **What buyers say about vitamin d 400iu**
What buyers praise and complain about, mined from review topics.
### **What buyers love **
**Value For Money**29%
*“Good Value”*
**Vitamin**14%
*“Overall, this seems like a good basic vitamin D supplement”*
**Ease Of Chewing/Swallowing**13%
*“ideal to swallow”*
**Quality-Overall**10%
*“Quality feels reliable and consistent, and the bottle has lasted well with regular use”*
**Advertised Vs Actual Product**6%
*“Does the job”*
**Ease Of Use**2%
*“Easy to take”*
**Dosage**2%
*“piece of mind that I'm not over doing it on dosage, so highly recommend”*
**Efficiency**2%
*“Definitely works”*
**Size-Overall**1%
*“I was pleasantly surprised by the size”*
**Taste-Overall**1%
*“no weird taste or smell”*
### **What buyers complain about **
**Size-Overall**14%
*“The capsules are small”*
**Dosage**11%
*“Slightly bigger tablets than I expected for this dose”*
**Vitamin**8%
*“Don't get nearly enough vit D via the sun”*
**Functionality-Overall**5%
*“96 doesn't work”*
**Ease Of Chewing/Swallowing**3%
*“I find tablets are always harder to swallow than capsules”*
**Ingredients-Overall**3%
*“Never again - this ingredient should be banned”*
**Quality-Overall**2%
*“cheap”*
**Side Effects**2%
*“Maltodextrin side effects - just awful”*
**Natural Resource Wastage**2%
*“A record-breaking waste of container space”*
**Design-Overall**2%
*“bad design”*
## **Common questions**
- **Is vitamin d 400iu profitable to sell on Amazon United Kingdom?**
- The niche generates £39K/yr across 4 tracked products. 0 of 1 products launched in the last 360 days are still selling. 90-day search growth is -49.0%. Flapen's verdict: Skip it (27/100).
- **How competitive is the vitamin d 400iu niche?**
- 4 brands and 16 sellers compete. The top 5 products take 100% of clicks and top 5 brands hold 100% of demand.
- **What do buyers complain about in vitamin d 400iu?**
- Top complaints mined from reviews: Size-Overall, Dosage, Vitamin. The return rate is 0.0%.
- **When does demand for vitamin d 400iu peak?**
- Demand peaks in Jan–Feb–Oct–Nov; the busiest month runs 2.8× the quietest.
- **What does it cost to enter the vitamin d 400iu niche?**
- Listings span £2.63–£7.03; the average listing price is £4.03 (sweet spot $15–$100). The average incumbent carries 1,793 reviews — the moat a new listing must climb.
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