This is the place to learn about Class 4 Lasers vs Class 2 or 3 lasers to help you to determine which laser system is the right fit for your needs and budget

Class 4 Laser functions chart
4 laser wavelength descriptions
laser functions on knee

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When is a Class 4 Laser System the best choice? 
Class 4 lasers are preferred for users who:

  1. Want to have the option of higher dosage, which is translated to joules per cm squared (j/cm2)
  2. Want to have the shortest treatment times (higher power translates to shorter treatment or more j/cm2 in a given time)
  3. Want to treat larger areas such as in neuropathy (due to fast treatments, can quickly move from one zone to the next)
  4. Want superior pain control through increased power and depth of penetration (Class 4 lasers are proven to deliver more energy deeper than cold lasers or class 3b laser)
  5. Will be treating a wide variety of soft and hard tissue injuries and issues with both high and medium dosages at either Continuous Wave (CW) or Pulsed Wave.
  6. Need to treat very deep areas and prefer 2-3 Infrared wavelengths that work simultaneously together to produce superior results.
  7. Have a higher volume practice 
  8. Can afford a higher end laser
Class 4 laser therapy system are much like other lower power systems except they deliver the energy faster, and they typically warm the tissue, which feels good to the patient and builds confidence because it is obvious that the treatment is in process. Dramatic pain relief and increased range of motion is often experienced within minutes.

In cases where the energy needs to be delivered over a large or deep area, this extra power keeps the treatment times less than 12 minutes and often only a couple of minutes per point or location, allowing the ability to cover more areas. The extra power also allows practitioners to deliver class 3b dosages in 1-2 minutes or go to higher dosages for superior pain control. Most practitioners prefer having the choice to treat larger areas faster and deeper, and provide better, faster pain control

Laser Therapy Science and Clinical Studies an online book of compiled clinical laser studies from around the world

There are 3 potential downsides to Class IV Laser Systems that you have to adjust to:

  1. They are more expensive than class I, II and 3b systems
  2. They must be kept moving (in general) if delivering over about 4 joules/second, except LZR7, which runs cooler than other class 4 lasers
  3. They have a higher risk of eye damage. This is extremely low if everyone wears safety glasses.

Class 4 Laser Systems Over 60 Watts

Not all class 4 system are alike. Admittedly there is some bad press about class 4 lasers, which is mostly about systems over 60 watts. Once you get into systems that deliver over 60 joules/second, you must keep the system moving quickly or you risk burning the the skin. However, with proper training and use the benefit comes for those who need the deepest penetration and saturation of deep target tissues. The higher power = higher photon density translates to superior penetration and delivery of therapeutic healing energy to deep target tissues. Our high power class 4 laser systems have become increasingly sought after as the words gets out about the advantages of high power. Customers love our 45 and 60 Watt Class IV lasers, which are popular for practitioners who want more power with the highest photon density for the deepest penetration. We offer two of the best 60 Watt Class 4 lasers in the industry. The REMY FX60 60 Watt Dual and the REMY ProMax 60W Dual. And for those who want a happy medium, the REMY FX45 45 Watt TriwWave laser runs warm but not hot, so it’s very comfortable for the patient and the user.

Understanding and Clarity Regarding Class 4 Laser Fear Inducing Claims

Below is a table that shows some common claims and some of the underlying facts behind the claim. Always keep in mind that almost every class 4 laser has the option to turn down the power when it is appropriate, so you actually have a lot of flexibility with a higher power pulsing or Continuous Wave (CW) class 4 therapy laser.



There is a big difference between class 3 and Class 4 products.

Yes and No.
Yes. Once you get above 5 Watts, the laser diodes are installed in a cooled housing and a fiber optic cable is used to transfer the power to the handheld probe/emitter. This adds complexity and expense to the system, and is another feature that adds to the additional cost of class IV lasers.

No, the general cutoff for a class 4 laser is 0.5 (1/2) watts per beam. The LZR7 is typically considered a Class 4 laser, but it also works with class 3b probes/emitters. The LZR7 probe emitters are similar to the Class 3b probes used by Thor laser, Apollo laser and other laser manufacturers that don’t use fiber optic cables. One simply chooses the individual laser probe desired, with diodes above or below .5 watt output. The line between class 3 and class 4 lasers is a matter of preference, time available to give treatments, purpose, power output desired and of course budget. We advise getting the most power you can afford between 30 and 60 Watts with 2-4 wavelengths to get the superior results and have the best, most efficient and effective experience.

Class 4 lasers are not appropriate for home use.

Most class 4 laser systems do require extra training to make sure the user is safe. Many home users start out getting therapy in a doctor’s office, but then want the convenience of therapy at home. By getting a prescription from a practitioner, we can make the class 4 laser available for personal use. Then the home user can adopt the protocol that is already working for use at home, in order to save time and increase treatment availability in the comfort of home. Systems such as the LZR7 Cool laser systems use a divergent beam and a timer as the main variables, consequently requiring less training as they produce insignificant amounts of heat. For pain control, continuous wave, class 4 power lasers are a top choice in the industry. For REMY Class 4 laser home user customers who have an RX from their doctor or chiropractor, we can help you with free customized training with a highly trained doctor (over 36 years experience in the field).

You can purchase a class 4 laser for equine, pet and veterinary laser use without RX. Class IV Lasers for personal use are available with an RX prescription from a Doctor or Chiropractor. Once you have your prescription, give a call at 1-800-575-7963 to discuss product options and prices. Training with a Dr will be included at no additional cost to ensure proper use and safety.

Too much power is not as effective for healing.

This statement has NOT be proven by an independent study; it has only been shown by studies paid for by lower power laser manufacturers who use the study to discredit class 4 systems. Higher dosages are better for pain control but higher-end Class 4 lasers have adjustable power so when you want less power, you simply turn it down. When you need more power for better pain control, you turn it up. The results are in and high end pain control centers now depend exclusively on Class 4 Therapy Lasers with power of 30-60 Watts in 2, 3 or 4 wavelengths to produce superior results.

The Arndt-Schulz curve that everyone uses to show the biphasic response of lasers has no numbers on it and there is very little information about the dosage at the peak. Current research has discredited that old theory and shown that superior results can be achieved for numerous physical issues by delivering considerably more power to target tissue than was previously believed necessary or desirable. Thus, the class 4 therapy market is large and growing as the exceptional results they produce are indisputable at this point. For both Practitioners and Clients the very high percentage of successful treatments for a wide range of issues in both humans and animals is exciting and satisfying.

Class 4 lasers are not worth the money.

For many people, higher dosages and shorter treatment times are a key to greater results. If you are not concerned about therapy times, flexibility or giving your patients the maximum pain relief, then a lower power product is fine. Class 4 lasers are for practitioners and home users who want to have every option available without limitations for any condition. State-of-the-art class 4 lasers can be purchased for much less than was previously in the last decade. We now have smaller, lighter class 4 lasers with more power and features than were previously available at prices that are $10k to $20k less expensive. offers exceptional class IV laser therapy devices at price between $8,950 to $25,000. 

REMY and Medray class 4 laser systems are exceptional, feature rich, highly effective, versatile and and worth every cent. They deliver high end quality and performance with a 5 year manufacturer warranty and free training. By cutting out the middle-man and the high overhead of boots on the ground distributors,  expensive showrooms and costly advertising we significantly reduce costs compared to the top name-brand class 4 lasers such as Aspen, Eltech K-Laser, Summus, Lightforce and others. This saves you money because they have to charge significantly more due to high overhead and high commissions paid to the traveling distributors. Brands such as REMY and Medray provide comparable power, wavelengths and higher end features with 30-50% less expense.

Class 4 lasers are better for pain control.

Class 4 lasers have shorter therapy times.

Class 4 lasers are better for treating larger areas.

Photon density dictates depth of penetration.

Yes to all of these claims.
Higher power lasers provide better pain control in a shorter period and can cover large areas with superior penetration, much faster than lower power lasers. The key here is not necessarily the class but the total power output of the system. Higher power allows for more flexibility. Everyone in the market seems to agree that more power is better for pain control, better for larger areas and will shorten the time it takes to get the optimum healing or pain control density.

Class 4 laser are dangerous.

Yes – potentially.
In the wrong hands, a class 4 cold laser can cause damage just like a scalpel, a bad drug prescription or any of the other tools doctors use every day. This is not a good reason to not have the tool. With proper training and adherence to safety precautions, class 4 lasers up to 60 watts are quite safe.

We do not typically recommend systems over 60 watts because the level of training and awareness is so high that it is not worth the extra money and risk to work at these power levels. Additionally,  there really is such a thing as working too fast. A patient has to feel like they are getting their money’s worth.

All the other products on the market are inferior to (insert product name here).

Though some manufactures may claim they are superior, there is not one solution that is the best for all applications. Every manufacturer has a unique value proposition. It is our job to help you find the most appropriate system for your application, needs and budget. 

Call a laser specialist for FREE Concierge service and support to help you determine the best laser for your needs and budget.
Call Toll Free 1-800-575-7963

What conclusions can we make about class 4 lasers?

The difference between a class 4 laser and class 3b laser is clear. Cold lasers such TerraQuant, MR4, Apollo, PowerLaser, Thor laser and LZR7 class 3b systems cost less because you deliver less power, less performance and reduced results. Because cold lasers and class 3b lasers are built with lower power diodes, less power, smaller housing and fewer options, without a  fiber optic design, it costs less than most comparable powered fiber-optic based class IV laser systems. The LZR UltraBright class II light therapy system is the only non-class 4 light therapy product that we endorse as producing similar amounts of power as a Class 4 laser, because it is made by a class 4 laser manufacturer and they figured out how to deliver true Class IV power in 10 or 20 Watts of optical power using a lower cost system with optical LEDs. They are ideal for home use and animal use consumers who want the power of class 4 but the safety of Class II.

Class 4 lasers may be the ultimate therapeutic laser for many applications but that really depends more on the requirements of the practice and practitioner. After 20 years of diligently working in the field testing and marketing all of these and many other laser therapy systems we are excited to report that Class IV Laser therapy systems typically outperform everything else. We like the Remy and Medray Class IV laser systems because they do everything that the more expensive class 4 laser brands do, for about half the price. Plus, they are the newest and most advanced models with the most current technological advancements, making them much more compact, lightweight and user friendly, with all the bells and whistles typically found in much more expensive laser systems.

The bottom line is that class 4 laser systems deliver results quickly, with the deepest penetration and are especially great for pain relief.
With 2 or more wavelengths they become more versatile and effective for regenerative healing. Some of them such as the REMY LASER work very well for pain relief, regenerative healing and can also be applied to the practice of minor surgical applications in Podiatry and Veterinary Medicine. Many people that don’t get results with a class 3b laser and below, will get results with a class 4 therapeutic lasers. That is why they are used in thousands of chronic pain clinics, Chiropractic offices and Physical Therapy rehab facilities in the US and throughout the world.

Call a Class 4 Laser Specialist Today

Free Concierge Service and Support with a Laser Specialist, Mr Kalon Prensky

How do you choose a laser for your practice?


Pulsed Wave, CW or Super Pulsed Laser, which is better?


Class 4 Lasers vs SuperPulsed Lasers and Cold Lasers – How do you choose?

Cold Lasers and Class IV Lasers emit light via laser diodes in three primary methods:

  1. Continuous Wave (CW)
  2. Pulsed Wave (PW)
  3. Super Pulsed Wave (SPW)

Continuous wave therapy lasers emit a beam of light that is uninterrupted and constant.
Pulsed wave therapy lasers cycle on and off in different ways and at different rates.
Super pulsed laser waves come from semiconductor laser diodes that typically only emit light pulses at 1,000th of a second, meaning its duty cycle is around 0.001% and average delivered power for a 25W super pulsed laser would be just 7-12mW.

Class 4 Lasers are most commonly available with laser diodes that can deliver CW or PW but do not offer super pulsing. CW lasers deliver the most therapeutic laser power to the target tissue than any other method, however the speed of delivery is dictated by the power of the laser diodes (measured in milliwatts (mW) and Watts (W). There are 1000mW in 1 Watt. Higher powered Class 4 lasers offer high speed photon delivery to target tissue, which makes it possible for busy therapists to effectively treat challenging musculoskeletal and soft tissue injuries within minutes. The higher the power in Watts, the faster the laser works. However, many practitioners like the therapeutic benefits that can be achieved from the addition of Hz frequencies. Utilizing these pulsed waves can double treatment times but offer additional frequency medicine benefits. Thus a 3 minute treatment with CW could be increased to a 6 min treatment with PW at 50% duty cycle:

  • Class 4 Lasers – Choose from Over 20 Models of the best, most power and cost effective, FDA 510k Class 4 lasers that are on the market today.

Pulse Parameters

All pulsed wave therapy lasers cycle on and off while operating – this cycle is called a “pulse”.   However, the length of time that the laser is emitting light and turned off during each pulse varies between lasers. We can understand the length and frequency of a pulsed wave laser’s on and off cycles using the following parameters:

Pulse Duration (PD)

The amount of time, in seconds, that the laser is emitting light during each pulse.

Pulse Interval (PI)

The amount of time, in seconds, that the laser is off (not emitting light) during each pulse.

Pulse Frequency Rate (PFR)

The number of pulses (on and off cycles) that a pulsed wave laser goes through each second. This parameter is measured in hertz. Keep in mind that hertz are equivalent to cycles per second – so a laser with a PFR of 7Hz is emitting 7 pulses per second.

Duty Cycle (DC)

The Duty Cycle (DC) is the pulse duration (PD) multiplied by the Pulse Frequency Rate (PFR). A duty cycle is expressed as a percentage or a fraction and can be determined with the equation DC = PFR X PD

Duty Cycle Equation:


The duty cycle tells us the percentage of time that a pulsed wave laser is emitting light while operating. However, the duty cycle does not tell us the power output that a pulsed wave therapy laser is emitting while operating. 
For example, a pulsed wave laser with a duty cycle of 50% (or ½) is emitting light only half of the time while in operation.

Peak Power

The maximum power output, in watts, that a laser diode is capable of emitting

Average Power – this is the true telling variable that has many people confused.

The average power output, in watts, that a laser diode is capable of emitting over time.

It’s important to identify the average power output of a pulsed wave therapy laser because laser therapy dosage is based on energy density.

This means that when a clinician keeps track of the Joules/cm2 being delivered to a patient, they account only for the average power output – not the peak power.

Average Power Equation:

Average Power = Peak Power x PFR x PD

Identifying the average power output of a pulsed wave therapy laser allows us to determine the energy density of a dosage delivered to a patient.


Hz Pulsed Therapy Lasers vs Super Pulsed Therapy Lasers

Pulsed wave therapy lasers are either:

  1. Chopped or Super Pulsed – with SP lasers the peak power can be quite high, rivaling the best class 4 lasers, however, the pulses are at a mere billionth of a second, which results in an average power output that is drastically low, typically averaging in the 5-50mW range at best. This is the reason that SP lasers never utilize standard laser protocols that requirements in joules/cm2.

A chopped pulse wave therapy laser is essentially a continuous wave therapy laser that uses a pulse generator to turn it on and off at programmed intervals.

This is different than Super Pulsed lasers, which use semiconductor laser diodes. A semiconductor diode creates a high-wattage output for a very short duration followed by an extremely long cool-down period.

A Super Pulsed laser diode will typically emit light for about 1,000th of the time it is in operation, meaning its duty cycle is around 0.001%. This is why they utilize much higher powered laser diodes or they wouldn’t work in comparison to the most common types of Cold Lasers that range in power from 5mW to 500mW and sometimes when they bundle multiple diodes they get up to 2400mW (2.4 Watts).

There is a significant difference of price between Class 4 Lasers and Super Pulsed Lasers which are often considered Class II. Class 3b Cold Lasers are Typically Use Near InfraRed (NIR) Laser diodes and Produce a maximum power output of 500mW per diode and up to 750mW if 

Some brands of class III therapy lasers use a superpulsed gallium arsenide (GaAs) laser diode with a peak power output of 25-watts. While that may sound impressive, keep in mind that this GaAs superpulsed laser diode is only capable of emitting 25-watts of power in brief, 200-nanosecond bursts, with a duty cycle of 0.001% – resulting in an average power output of less than 25mw (0.25-watts).

Understanding the difference between peak power output and average power output is key when reviewing pulsed wave therapy lasers. Many manufacturers like to boast about the high-wattage peak power outputs of their Super Pulsed laser diodes without being upfront about the average power outputs of their devices. Don’t be fooled into thinking that a 25-watt Super Pulsed laser can deliver therapeutic results that are comparable to those you will see from a 25 Watt continuous wave therapy laser. There is a reason that the Super Pulsed Lasers are significantly less expensive that Class 4 Lasers. When a person invests in a therapeutic laser they have to weigh the pros and cons including the typical duration of treatment, which determines how much laser therapy you can deliver in a given amount of time. That said, if you want the fastest high quality treatment every time, then investing in a powerful class 4 laser with the most power you can afford up to 45 Watts is key. Any more than that is not necessary, nor desirable since psychologically if a laser works too fast it becomes hard to believe. 

If you have significantly more time to use the laser or you want it just for home use or you simply can not scrape the money together for a class 4 laser, then a higher powered Class 3b CW & PW laser or a Class II Light Therapy Device such as the LZR UltraBright 10-20 Watt could be a good choice. The good ones do produce high quality clinical results with the delivery of a sufficient dose of photonic energy, which is measured in joules per cm squared (j/cm2). We are happy to help you to get a laser light therapy device that will meet your needs and budget. 

You can get the individualized support that you need by calling a laser specialist for Complimentary Concierge Service and Support at Discover Lasers LLC. 
Ph 800-575-7963


  • Class 4 Lasers – Choose from Over 20 Models of the Best & Most Affordable Class 4 Lasers 
  • the LZR UltraBright 10-20 Watt – Choose from 2 Models of the Most Powerful, Fastest Working, Class II Light Therapy Devices that have ever been made.