Key takeaways.
- HILT, HPLT, high-power laser, and Class 4 laser all describe the same treatment.
- Class 4 is a safety classification under IEC 60825-1. It describes eye hazard, not clinical quality.
- The mechanism is photobiomodulation: light absorbed by mitochondria, shifting cell behaviour toward repair.
- More power means more energy reaching deep tissue in the same time. Dose at the target is what decides the result.
The naming problem, cleared up.
If you have called around a few clinics you have probably been given four different names for what turned out to be the same machine. High-intensity laser therapy, or HILT, is the phrase the European research literature settled on. High-power laser therapy, or HPLT, is what North American clinics tend to print on their websites. Class 4 laser is a description of the device’s safety rating. Photobiomodulation is the name for the biological effect all of them are trying to produce.
None of these terms is more advanced than the others. They are regional and disciplinary habits. When a clinic markets “HILT” as though it were a distinct, newer technology than the “Class 4 laser” down the road, that is a marketing choice rather than a technical distinction.
What “Class 4” really tells you.
Laser classes come from IEC 60825-1, the international standard for laser product safety. The classes run from 1, which is safe under all reasonably foreseeable conditions, up to 4, which is the highest hazard category. A Class 4 laser can injure the eye and can, in principle, burn skin or ignite material if misused.
So the class number is a hazard rating. It tells you the room needs controls and everyone in it needs eyewear. It does not certify that the treatment works, that the operator is skilled, or that the device is well suited to your injury. A clinic advertising “Class 4” as if it were a quality mark has confused a safety label for a clinical one.
What the higher class does imply is higher optical power, and that has a genuine practical consequence. More power delivers more photons to a given depth in the same amount of time, which is what makes deep targets treatable within a session length anyone would sit through.
What the light does once it is inside you.
Therapeutic lasers work in the red and near-infrared band, roughly 600 to 1000 nanometres. That range is chosen because skin lets it through comparatively well and because your cells contain something that absorbs it.
That something is cytochrome c oxidase, an enzyme sitting in the mitochondria. When it absorbs these photons, the cell briefly produces more energy and the local chemistry that sustains inflammation is altered. The mechanisms proposed for this are reviewed by de Freitas and Hamblin (2016), which remains the standard reference for how photobiomodulation is thought to work.
Two honest caveats. First, the effect is temporary, which is why a course rather than a single session is the norm. Second, the mechanism being real does not by itself tell you the treatment produces a meaningful clinical result for your particular injury. That question is answered by trials, not by biology, and we deal with it on the evidence page.
What it is not.
A therapeutic laser is not a surgical laser. Surgical devices are built to cut and coagulate using concentrated heat. A therapeutic device is built to deliver light that alters cell activity, and the handpiece is kept moving so heat never concentrates. Warmth during a session is normal. Burning is not, and it means something needs adjusting immediately.
It is also not the same as the red light panels sold for home use. Those use LEDs scattering low-power light across a wide area, which can reach skin-level targets. Getting a comparable dose into a tendon several centimetres down is a different engineering problem, and a panel does not solve it.
Finally, it is not a replacement for loading. Laser lowers pain and irritability for a window of time. What changes a tendon or a stiff joint over months is progressive exercise. The laser buys you the comfort to start that work sooner.
Who regulates the device in Canada.
Laser products sold, leased, or imported into Canada fall under Health Canada’s laser product regulations, which cover a broad range of devices and place compliance obligations on the manufacturer before a product reaches the Canadian market.
Separately from the device, the person operating it is regulated. Physiotherapists at Medstar are registered with the College of Physical Therapists of British Columbia, and you can look up any of them by name in that public directory.
Frequently asked questions.
What is high intensity laser therapy?
High intensity laser therapy is a physiotherapy treatment that delivers red and near-infrared light into tissue at therapeutic power levels. The light is absorbed inside your cells, mainly by an enzyme in the mitochondria, which temporarily shifts the local cell environment toward repair and away from inflammation. The formal term for the effect is photobiomodulation. It is delivered in slow passes over the skin and takes 10 to 20 minutes.
What is the difference between HILT, HPLT, and Class 4 laser?+
HILT, HPLT, and Class 4 laser all name the same treatment. HILT stands for high-intensity laser therapy and is the term European research papers prefer. HPLT stands for high-power laser therapy and is more common in North American clinics. Class 4 is the device's safety classification. A clinic advertising any of these three is describing the same machine and the same treatment.
What does Class 4 mean on a therapeutic laser?+
Class 4 is the highest hazard category in the international laser safety standard IEC 60825-1, which classifies lasers by the risk they pose to eyes and skin. It means the beam can cause eye injury and requires controlled conditions and protective eyewear. Class 4 is a safety label rather than a clinical grade, so it describes the hazard the device presents, not how effective the treatment will be.
Is Class 4 laser better than cold laser?+
Class 4 lasers deliver more optical power than cold lasers, which are Class 3B and below, so more light energy reaches deeper tissue in the same treatment time. That matters for structures under skin and fat, like a hip tendon. What decides the clinical result is the dose actually delivered to the target, so a well-dosed Class 3B session and a well-dosed Class 4 session can both work.
How does laser light change anything inside the body?+
Red and near-infrared photons pass through skin and are absorbed by cytochrome c oxidase, an enzyme in the mitochondria of your cells. That absorption briefly increases cellular energy production and alters the signalling chemistry that sustains local inflammation. The proposed mechanisms are set out by de Freitas and Hamblin in a 2016 review. The effect is biological and temporary, which is why treatment is repeated across a course.
What wavelength does therapeutic laser use?+
Therapeutic lasers operate in the red and near-infrared part of the spectrum, roughly 600 to 1000 nanometres, because that range passes through skin most readily and is absorbed well by mitochondria. Different wavelengths penetrate to different depths, so a device treating a deep hip structure uses a different setting than one treating a superficial finger tendon. Your physiotherapist selects the setting for the target tissue.
Does high intensity laser cut or burn tissue?+
No. Surgical lasers are designed to cut and coagulate tissue with concentrated heat, and therapeutic lasers are built for a different purpose entirely, delivering light at levels intended to alter cell activity rather than destroy tissue. You feel warmth during a therapeutic session because some energy converts to heat, but the handpiece keeps moving specifically so that heat never concentrates in one spot.
Is laser therapy the same as red light therapy panels?+
They share a mechanism but differ in delivery. Consumer red light panels use LEDs that scatter light broadly at low power across a wide area. A therapeutic laser produces coherent light focused through a handpiece at far higher power, so it reaches deeper structures. A panel may help superficial skin-level targets. It does not deliver a comparable dose to a tendon sitting under several centimetres of tissue.
How deep does high intensity laser penetrate?+
Penetration depends on wavelength, power, and what sits between the handpiece and the target, so body composition changes the answer for the same device. Near-infrared wavelengths reach deeper than red ones, and higher power drives more photons through the same tissue. This is the practical argument for a Class 4 device: deep targets like a gluteal tendon or the back of a knee joint receive a meaningful dose within a realistic treatment time.
Is high intensity laser therapy regulated in Canada?+
Yes. Laser products sold, leased, or imported in Canada fall under Health Canada's radiation-emitting device regulations, and manufacturers must ensure compliance before a device reaches the market. Separately, the physiotherapists who operate the device at Medstar are registered with the College of Physical Therapists of British Columbia, which governs their scope of practice and conduct.
Sources.
- de Freitas LF, Hamblin MR. Proposed Mechanisms of Photobiomodulation or Low-Level Light Therapy. IEEE Journal of Selected Topics in Quantum Electronics (2016)
- IEC 60825-1: Safety of laser products, equipment classification and requirements
- Health Canada: Laser products, scope of the regulations
Sources checked 4 September 2026.
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Reviewed by Sanaz Davarian, PT, MSc, Owner & Director, Registered Physiotherapist, College of Physical Therapists of British Columbia (CPTBC). Medstar was the first physiotherapy clinic on the North Shore to install a Class 4 high intensity laser.
This page is for general information only and does not constitute medical advice. High intensity laser therapy is one tool among several, and it is not appropriate for every injury or every person. Nothing here is a promise of a particular outcome. Treatment suitability is determined case-by-case during clinical assessment. Physiotherapy at Medstar Sport Physio & Health is provided by physiotherapists registered with the College of Physical Therapists of British Columbia (CPTBC).