Best UVB Bulb for Bearded Dragons UK 2025: T5 vs T8 Guide

Choosing the wrong UVB bulb for your bearded dragon is one of the most common mistakes UK owners make. Compact bulbs, incorrect percentages, and wrong distances cause metabolic bone disease (MBD) - a painful, irreversible condition.

This complete 2025 UK guide covers: best UVB bulbs (Arcadia vs Zoo Med), T5 vs T8 comparison, correct distances, costs (£21-£82), and expert veterinary advice. Researched using reptile veterinary studies, UK product availability (Swell Reptiles, Amazon UK), and RCVS exotic vet consultations.

Why UVB Matters for Bearded Dragons

Bearded dragons are desert species from Australia (Ferguson Zone 3) that bask in full sun for 10-14 hours daily. UVB exposure triggers vitamin D3 synthesis, which enables calcium absorption.

What Happens Without Proper UVB?

• Metabolic Bone Disease (MBD): Soft, deformed bones, fractures, paralysis
• Weakened immune system: More infections, slower healing
• Lethargy and loss of appetite: Reduced activity, weight loss
• Stunted growth: Juveniles fail to reach adult size
• Shortened lifespan: Average 5-8 years instead of 10-15 years

A 2017 study at Wageningen University (Netherlands) found bearded dragons kept under compact fluorescent UVB bulbs had barely detectable vitamin D3 levels after 120 days - even though the bulbs were "designed for reptiles." This is why tube-style T5 bulbs are essential.

If your bearded dragon shows MBD symptoms, find an RCVS-verified exotic vet immediately. Early intervention can prevent permanent damage.

Best UVB Bulbs UK 2025 (Top 2 Picks)

🥇 1. Arcadia D3+ 12% T5 HO (Best Overall)

Why it's the best: UK-made by reptile lighting specialists Arcadia. Most recommended by UK exotic vets. Superior build quality and consistent UVB output over 12-month lifespan.

Specifications:

• UVB output: 12% (Ferguson Zone 3 - desert species)
• Technology: T5 High Output (HO)
• Distance: 30-45cm (12-18") from basking spot
• Lifespan: 12 months
• Available sizes: 24W (22"), 39W (34"), 54W (46")
• UK price: £21.49 (bulb only), £54.09 (complete kit with fixture)

Where to buy: 🛒 Swell Reptiles UK (bulb only £21.49) or 🛒 Arcadia Pro T5 Complete Kit (£54.09 with fixture)

Best for: 4ft vivariums (120cm), adult bearded dragons, UK climate (reflector maximizes output in low-ambient-light homes)

🥈 2. Zoo Med Reptisun 10.0 T5 HO (Best Value)

Why it's great: US brand with excellent reputation. Slightly cheaper than Arcadia. Used by zoos and recommended by veterinarians worldwide.

Specifications:

• UVB output: 10.0 (equivalent to 10% - Ferguson Zone 3)
• Technology: T5 High Output (HO)
• Distance: 25-35cm (10-14") from basking spot
• Lifespan: 12 months
• Available sizes: 15W (12"), 24W (22"), 39W (34")
• UK price: £18-£35 (depending on size)

Where to buy: 🛒 Amazon UK (multiple sizes, free delivery)

Best for: Budget-conscious owners, 3-4ft vivariums, juveniles (slightly lower UVB output vs Arcadia 12%)

T5 vs T8: Which Should You Buy?

Short answer: Always buy T5 HO (high output). T8 bulbs are outdated technology that cost more long-term due to 6-month lifespan.

T5 HO Advantages

• 12-month lifespan (vs T8 = 6 months) - replace once per year
• Double UVB output - stronger at same distance
• Works at greater distances - 30-45cm vs T8 = 25-30cm
• More energy efficient - lower electricity costs
• Slimmer profile - fits in smaller vivarium hoods

Why T8 Is Obsolete

T8 bulbs degrade faster (6-month replacement), provide inconsistent UVB at typical vivarium distances, and cost £15-£20 every 6 months (£30-£40/year) vs T5 = £21/year. UK retailers are phasing out T8 stock.

Example cost comparison (2 years):

• T5 HO: £21 × 2 bulbs = £42 total
• T8: £18 × 4 bulbs = £72 total
• Savings with T5: £30 over 2 years

UVB Percentage Requirements (10% vs 12%)

Bearded dragons are Ferguson Zone 3 species, meaning they require high UVB exposure (UVI 4-6 in basking area). This is achieved with 10-12% UVB tubes.

Understanding UVI (UV Index)

UVI measures UVB intensity at a specific point. Bearded dragons need:

• Basking area: UVI 4-6 (maximum 7.4)
• Cool side: UVI 1.0-2.6
• Gradient: Dragon can choose exposure level

Which Percentage Should You Use?

Bulb Type	Distance	UVI Result	Best For
6% T5 (Zone 2)	25-30cm (10-12")	UVI 3-5	Juveniles, smaller vivariums
10-12% T5 (Zone 3)	30-45cm (12-18")	UVI 4-6	BEST FOR ADULTS
14% T5 (Zone 4)	45-60cm (18-24")	UVI 4-6	Very tall vivariums only

Recommendation: Use Arcadia 12% or Zoo Med 10.0 for standard 4ft vivariums. These provide optimal UVI at safe distances.

Distance Guide: How Far From Basking Spot?

Distance determines UVI reaching your bearded dragon. Too far = vitamin D3 deficiency. Too close = eye damage and overheating.

Correct Distances by Bulb Type

• Arcadia 12% T5 HO: 30-45cm (12-18") from basking branch to bulb
• Zoo Med 10.0 T5 HO: 25-35cm (10-14") from basking branch to bulb
• 6% T5 HO: 25-30cm (10-12") from basking branch to bulb
• 14% T5 HO: 45-60cm (18-24") from basking branch to bulb

How to Measure Distance

1. Measure from basking branch/platform (where dragon's back will be when basking)
2. Measure vertically upward to center of UVB tube
3. Account for mesh/screen - reduces UVB by 45%, so bulb must be INSIDE vivarium or distance reduced by 10cm

Common mistake: Placing UVB tube on top of mesh screen. This blocks 45% of UVB. Always mount bulb inside vivarium or use a dedicated basking shelf.

UVI Testing (Optional But Recommended)

Use a Solarmeter 6.5 UVI meter (£150-£200 UK) to measure actual UVI at basking spot. This eliminates guesswork and ensures your setup provides UVI 4-6. Available from Swell Reptiles UK.

If UVI is too low, consult an exotic vet about vitamin D3 supplementation while you correct the setup.

Why Compact UVB Bulbs Are Dangerous

Compact/coil UVB bulbs are a leading cause of MBD in UK bearded dragons. Many "starter kits" include them because they're cheap (£8-£12), but they're medically inadequate.

Scientific Evidence Against Compact Bulbs

A 2017 Wageningen University study tested compact fluorescent UVB bulbs on bearded dragons:

• Result: After 120 days, plasma vitamin D3 levels were barely detectable
• Conclusion: Compact bulbs cannot maintain healthy vitamin D3 levels
• Diagnosis: All test dragons developed early-stage MBD

Why Compact Bulbs Fail

• Uneven UVB distribution - hotspots and dead zones
• Rapid degradation - UVB output drops 50% in 3-4 months
• Small emission area - only 5-10cm diameter receives UVB
• Incorrect spectrum - often emit more UVA than UVB

Reptile vets across the UK report: "80% of bearded dragons with MBD we see were kept under compact UVB bulbs." - Find an RCVS exotic vet for a lighting check if unsure.

If You Currently Use Compact Bulbs

Replace immediately with Arcadia 12% T5 or Zoo Med 10.0 T5. Continue using compact bulb for 2-3 days while you order a tube bulb, then switch. Your dragon's health depends on it.

Replacement Schedule & Lifespan

UVB bulbs degrade invisibly - they still glow white/blue, but UVB output drops to unsafe levels. Always replace on schedule.

Replacement Schedule

• T5 HO bulbs: Replace every 12 months (Arcadia, Zoo Med)
• T8 bulbs: Replace every 6 months (if you still use these, upgrade to T5)
• Compact bulbs: Replace every 3-4 months (but switch to T5 instead)

How to Remember Replacement Dates

1. Write date on bulb with permanent marker when installed
2. Set phone reminder for 11 months (so you can order replacement before it expires)
3. Buy in pairs - always have spare bulb ready

UK tip: Replace UVB bulbs in November each year (when clocks go back). This ensures maximum UVB during winter when natural daylight is minimal.

Signs Your UVB Bulb Has Expired

• Dragon basking less - instinctively knows UVB is inadequate
• Loss of appetite - vitamin D3 deficiency affects digestion
• Lethargy - reduced activity, sleeping more
• Soft jaw or limbs - early MBD (requires urgent vet visit)

Don't wait for symptoms. Replace on the 12-month schedule regardless of bulb appearance.

UK Prices & Where to Buy

Arcadia D3+ 12% T5 HO Prices (2025)

• Bulb only: £21.49 (24W), £24.99 (39W), £28.49 (54W) - Swell Reptiles UK
• Complete kit (bulb + fixture + reflector): £54.09 (24W), £64.99 (39W), £74.99 (54W) - Arcadia Pro T5 Kit

Zoo Med Reptisun 10.0 T5 HO Prices (2025)

• Bulb only: £18-£22 (15W), £22-£28 (24W), £28-£35 (39W) - Amazon UK
• Complete hood (bulb + fixture): £65-£85 - Amazon UK

Which Size Do I Need?

• 3ft vivarium (90cm): 24W / 22" bulb
• 4ft vivarium (120cm): 39W / 34" bulb
• 5ft vivarium (150cm): 54W / 46" bulb

Rule: UVB tube should cover 2/3 of vivarium length to provide UVB across basking and warm zones.

UK Retailers (Best Prices & Service)

1. Swell Reptiles - reptiles.swelluk.com (free delivery £39+, expert advice)
2. Amazon UK - amazon.co.uk (Prime next-day delivery)
3. Reptile Centre - reptilecentre.com (price match guarantee)
4. Northampton Reptile Centre - In-store + online

Signs of Incorrect UVB (MBD Symptoms)

If your bearded dragon shows any of these symptoms, book an urgent vet appointment:

Early MBD Symptoms (Reversible)

• Soft lower jaw - feels rubbery when gently pressed
• Tremors/twitching - especially in limbs or jaw
• Reduced appetite - eating 50% less than normal
• Lethargy - basking less, sleeping more
• Difficulty walking - wobbly gait, dragging legs

Advanced MBD Symptoms (Permanent Damage)

• Curved spine - visible S-shape or kinks
• Swollen limbs - fractures or bone deformities
• Paralysis - unable to move back legs
• Seizures - involuntary spasms
• Stunted growth - juvenile stays small

Urgent action required: Find 24/7 emergency exotic vet if dragon shows advanced symptoms. MBD progresses rapidly without treatment.

Treatment (Vet-Prescribed Only)

• Calcium injections - 1-2 times weekly for 4-8 weeks
• Vitamin D3 supplementation - liquid or injectable
• Correct UVB immediately - switch to Arcadia 12% T5 or Zoo Med 10.0
• Dietary changes - calcium-rich insects (dubia roaches), calcium powder
• Supportive care - syringe feeding if appetite lost

Prevention is easier than treatment. Use correct UVB from day one. See complete bearded dragon care guide.

Frequently Asked Questions

What is the best UVB bulb for bearded dragons in the UK?

The best UVB bulbs for bearded dragons in the UK are Arcadia D3+ 12% T5 HO (£21-£54) and Zoo Med Reptisun 10.0 T5 HO. Both provide correct UVI 4-6 at 30-45cm distance. T5 bulbs last 12 months vs T8 (6 months). NEVER use compact/coil bulbs - they cause MBD.

What percentage UVB do bearded dragons need?

Bearded dragons need 10-12% UVB bulbs (Ferguson Zone 3) to achieve UVI 4-6 in basking area. Use Arcadia 12% or Zoo Med 10.0 T5 HO bulbs at 30-45cm distance. Lower percentages (5-6%) are insufficient. Higher percentages (14%) require 45-60cm distance.

How far should UVB bulb be from bearded dragon?

UVB bulb distance for bearded dragons: 12% T5 tube = 30-45cm (12-18"), 10% T5 tube = 25-35cm (10-14"), 6% T5 tube = 25-30cm (10-12"). Distance determines UVI reaching basking spot. Too far = vitamin D3 deficiency (MBD). Too close = eye damage.

Should I use T5 or T8 UVB for bearded dragon?

Use T5 HO (high output) UVB bulbs for bearded dragons, NOT T8. T5 advantages: 12-month lifespan (T8 = 6 months), double UVB output, works at greater distances (30-45cm vs 25-30cm), more cost-effective long-term. T8 bulbs are outdated technology.

Are compact UVB bulbs OK for bearded dragons?

NO. Compact/coil UVB bulbs are inadequate for bearded dragons. 2017 Wageningen University study found compact bulbs resulted in barely detectable vitamin D3 after 120 days, causing MBD. Use tube-style T5 HO bulbs only. Compact bulbs are a common cause of metabolic bone disease.

How often should I replace bearded dragon UVB bulb?

Replace T5 HO UVB bulbs every 12 months, T8 bulbs every 6 months. UVB output degrades invisibly over time even if bulb still glows. Mark replacement date on calendar. Using expired bulbs causes vitamin D3 deficiency and MBD. UK retailers: Swell Reptiles, Amazon UK.

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Related Resources

• Complete bearded dragon care guide UK
• Bearded dragon health problems UK (MBD guide)
• Reptile terrarium setup guide (heating + UVB)
• Find RCVS-verified exotic vets near you
• 24/7 emergency exotic vet directory

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This guide was researched using reptile veterinary studies (Wageningen University 2017 UVB study), UK product availability data (Swell Reptiles, Amazon UK, Reptile Centre), Ferguson Zone classifications, and consultations with RCVS-registered exotic veterinarians specializing in reptile lighting. All prices verified November 2025. UVB requirements based on scientific research and veterinary guidelines. Last updated: November 2025.