UVB LED lamps: 18 models through the spectrometer, none matches the sun’s spectrum
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
Since 2019, UVB LED lamps have been sold in the reptile hobby as the modern successor to fluorescent tubes. A study published in 2024 by Wunderlich, Griffiths and Baines in Zoo Biology analysed their spectrum, and the result deserves to be known before you buy (see the study, doi 10.1002/zoo.21806). Our other equipment guidance is gathered in the reptile accessories section.
Contents · 6 sections
Eighteen lamps, not one solar spectrum
The authors measured the spectrum and mapped the irradiance of eighteen of these lamps. Their conclusion is unambiguous: the spectrum of every UVB LED tested bears little resemblance to the solar ultraviolet spectrum. This is not a one-off manufacturing defect, it is a property of the technology: an LED emits in a narrow band, where the sun and a fluorescent tube produce a continuum.
The missing band, 315-335 nm
The most important point is an absence common to all the lamps: none emits significantly between 315 and 335 nanometres. Yet this band is the one that lets a reptile naturally regulate its own cutaneous synthesis of vitamin D3, by degrading excess precursor instead of accumulating it. Without it, the biological brake cannot operate. The authors infer a possible risk of hypervitaminosis D — and they are explicit about the status of that inference: it is a hypothesis drawn from spectral analysis, and they call for long-term animal studies to test it.
A tissue-damage mechanism already documented
Some lamps also emitted short, non-terrestrial wavelengths known to cause acute photokeratoconjunctivitis; the authors report one such case. That this kind of radiation can harm a reptile is not theoretical: a report published in 2009 by Gardiner, Baines and Pandher described a ball python and a blue-tongued skink with three weeks of anorexia, lethargy and excessive shedding, with necrosis of the basal cells of the epidermis on histology in both animals; only the python additionally showed bilateral corneal opacity and ulcerative keratoconjunctivitis. An essential clarification: those cases date from 2009 and the lamp involved was not an LED. Analysis of one unit of the model concerned showed extremely intense ultraviolet radiation, including very short-wavelength UVB absent from sunlight. That report shows the mechanism exists; it does not prove that today’s LEDs trigger it.
What the study does not show
No reptile was exposed under a protocol in the 2024 work: it is an analysis of devices, not a clinical study. It therefore demonstrates neither hypervitaminosis, nor lesions, nor disease. The authors also deserve credit on a point the summaries forget: they note the real advantages of LEDs, namely their energy efficiency, the absence of mercury and the absence of a ballast. The message is not “LEDs are bad”, it is “the UVB LED is not yet the equal of a tube”.
What this changes when buying
As long as long-term studies are lacking, the cautious approach is to keep a continuous-spectrum UVB source for the species that depend on it, and not to replace a tube with a UVB LED purely because it draws less power. Our guidance on choosing a UVB lamp and on how often to replace a UVB bulb still holds. Our article on combined LED and UVB lighting has been updated in the light of these data.
Frequently asked questions
Should a UVB LED lamp already installed be thrown away?
The study does not allow a conclusion of proven danger: it describes an unusual spectrum and a hypothetical risk. The cautious reasoning is not to make it the sole UVB source for a sun-loving species, not to panic.
Does an ordinary lighting LED emit UVB?
An ordinary white lighting LED is not designed for that. UVB-emitting LEDs do exist, however, and have since 2019 — those are the ones the study analyses. Find all our guides on the reptile hub.
In our shop, for this use: Stick-on digital thermometer for aquarium and terrarium glass (€18.90) · the whole shop
This guide is part of Planète Pets’s Reptiles universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.
