Red Light Therapy Dose and Protocol | LightTherapy.no

The number on the box doesn't tell you what you need to know

You've bought a panel. Or you're about to. And somewhere on the website, or in the manual, there's a line that says "use for 20 minutes, 5 to 7 times per week." And you follow it, because what else are you going to do? The company said so.

Here's what nobody tells you: that number means almost nothing without three other pieces of information - your distance from the panel, your panel's actual irradiance output, and what you're trying to achieve. Miss any of those and you could be underdosing and wondering why nothing's happening, or overdosing and actively working against your own results.

Effective dosing in red light therapy isn't about minutes alone - it's about energy delivered to the tissue, measured in joules per square centimetre (J/cm²). The dose equals irradiance (mW/cm²) multiplied by time in seconds, divided by 1000. Distance matters because irradiance drops significantly as you move further from the panel. Skin tone matters because melanin absorbs more light. Your goal matters because skin-level effects need different parameters than joint or muscle recovery. "20 minutes, 5 times a week" without these variables is close to meaningless guidance.

I've been saying this for a long time, and I know it sounds like I'm making it complicated. I'm not. Once you understand the basic relationships, it becomes quite simple. Let me take you through it.

What dose actually means

Think of it this way: if you're trying to water a plant, "two minutes with a watering can" tells you almost nothing useful. How big is the can? How far away are you holding it? Is it the same plant every time or a different one? Dose in red light therapy works the same way.

The formula is: Joules/cm² = (mW/cm² × seconds) ÷ 1000

If your panel delivers 50 mW/cm² at 15 cm distance and you stand there for 10 minutes (600 seconds), your dose is (50 × 600) ÷ 1000 = 30 J/cm². That might be appropriate for one goal and too much for another. At 30 cm the irradiance might drop to 20 mW/cm², so the same 10 minutes gives you only 12 J/cm². Same session length, very different result.

Does this sound familiar:  you've been using a panel for weeks and wondering why you're not seeing what you expected? Distance is often the answer. Move closer and reduce time, rather than just running longer sessions further away.

The research-backed window for most therapeutic goals sits between roughly 4 and 30 J/cm², depending on the target tissue and condition. Below 4 J/cm² and you're often in the subclinical range. Above 30–40 J/cm² you risk running into the biphasic dose response, the point where more light starts to inhibit rather than stimulate. Dr. Michael Hamblin's work on this (PMID: 22461763) is the clearest reference point. Too much is genuinely not more. I've seen people abandon red light therapy because they were overdoing it and feeling worse, which is one of the more frustrating outcomes because the intervention itself was sound.

Distance, wavelength, coverage - why they all change the picture

Distance. Irradiance follows an inverse square relationship with distance - double the distance, roughly quarter the power per cm². This is why moving from 10 cm to 30 cm from the same panel isn't just "stepping back a bit." It changes your dose significantly. If you have a panel with high irradiance and you're standing close, you might need surprisingly short sessions. If you're further away, you need longer. The company's claimed irradiance figure is usually measured at a specific distance, check what that is.

Wavelength. Wavelengths matter for penetration depth. Red light at 630–660 nm penetrates to roughly 5–10 mm. It's effective for skin-level work, surface wounds, and thin muscle tissue. Near-infrared at 800–850 nm penetrates deeper, reaching joints, thicker muscle groups, and connective tissue. For joint issues; knees, ankles, shoulders,  you want near-infrared in your panel. At 810 nm specifically, there's evidence suggesting slightly deeper penetration than 850 nm, which is worth knowing if you have deep joint problems. Most quality panels combine both, which gives you coverage at multiple depths.

I'll be honest about something here: when companies say "clinically studied wavelengths" and list 850 nm, they're not being dishonest,  850 nm is well studied. But it's also the cheapest wavelength to source, which means some panels use it heavily not because it's the best choice but because it's economical. I test everything with a spectrometer before stocking it. The spectral distribution matters, and the actual output should match what's claimed. (I've talked about this on Instagram @home_light_therapy,  there are spectrometer readings from various panels if you want to see them side by side.)

Coverage. A larger panel gives you systemic exposure,  your whole torso, or most of it, in a single session. This drives whole-body effects: circulation, inflammation reduction, energy. Smaller targeted devices go deeper locally but don't give you systemic benefit. Which do you need? For energy, sleep, and general recovery, systemic is usually what you want. For a specific joint or injury site, targeted makes sense. Many people end up with both eventually, which is very much an "I'm one of those people now" moment I remember clearly.

Skin tone, seasons, and the variables that change

Here's something almost nobody selling panels in Norway mentions: melanin absorbs red and near-infrared light. If you have darker skin, more of the light energy gets absorbed before it reaches deeper structures. This doesn't make red light therapy less effective for people with darker skin,  it means you may need slightly more time or closer distance to deliver the same effective dose to the target tissue.

And seasons. I genuinely use my panels differently in July than in January. In summer, I'm outside more, getting natural near-infrared from the sun, and I use the panel targeted for specific recovery work after training. In winter,  when I'm indoors more, when my baseline light environment is fundamentally different - I use it more systemically. Morning sessions as a substitute for the morning solar exposure that's driving circadian signalling and mitochondrial function during summer. Have you thought about that? The light you get from outdoor sun in summer contains near-infrared. Indoors in winter, it doesn't. Your panel can bridge some of that gap. I've written about this seasonal shift in more detail in the post on why summer and winter call for different strategies - it's worth reading alongside this one.

Performance and recovery — what the studies actually show

For muscle performance and delayed onset muscle soreness (DOMS), the evidence is solid. A meta-analysis (PMID: 29090398) found consistent improvements in muscle performance, reduced DOMS, and faster strength recovery when dosing was within the appropriate range. A separate study on 660 nm and 830 nm specifically (PMC: PMC3282894) showed both wavelengths delay fatigue and support performance,  but the key phrase in both papers is "when dosing parameters are correct."

A review specifically on parameters (PMC: PMC8355782) makes this point directly: irradiance, fluence, and area dictate the outcome. This isn't a caveat in the fine print. It's the central finding.

For a leg day session specifically, using the panel before training at 5–12 J/cm² per muscle group (quads, hamstrings, calves) tends to shift peak soreness earlier, so it hits hardest on day one rather than building through to day two or three. Post-workout at 6–10 J/cm² adds a second layer of recovery support for heavier loads. I sometimes add a near-infrared only session in the evening if I've had a hard day. Later enough not to affect melatonin production, because red light at night is a different conversation. The full protocol breakdown for DOMS specifically is in the post on red light therapy for post-workout muscle soreness.

If you want to go deep on what "50 mW/cm²" means and why not all measurements are created equal, the post on irradiance measurement covers this in detail. And the follow-up on factors affecting light penetration takes it further - skin thickness, hair, tissue type, all of it.

Building your starting protocol

This is where I'd start if you came to me with a new panel and asked what to do. Not as a rigid prescription -  as a framework you'll adjust based on how your body responds.

Start conservative: 4–8 J/cm² per target area, 1–3 times per week. Get a sense of how you respond before adding more. Over two to three weeks, you can move toward 10–20 J/cm² if you're tolerating it well and want more effect. Stay below 30 J/cm² as a general rule;  you can find the Arndt-Schulz curve references at the bottom of this post if you want to read the mechanism.

Choose your distance: 10–30 cm for most full panels with reasonable irradiance. 2–10 cm for smaller handheld devices. If you feel drowsy or unusually flat after sessions, you're probably overdoing it, back off on time or move further away before your next session.

Evaluate after two to three weeks. Better sleep? Less DOMS? More energy? Those are your signals. Adjust frequency rather than duration first if you want to increase the effect.

For systemic benefit,  energy, recovery, general support,  the panels in our full-body panel collection are where to start. For targeted joint or muscle work, the portable and specialist devices are more practical.

Want me to work out an accurate protocol for the specific device you have or you're considering? Tell me the model, your goals, and I'll give you actual numbers for time, distance, and frequency. That's what I'm here for. Not just the sale-  the bit after.

This post is educational and not medical advice. Individual responses to red light therapy vary. The biphasic dose response means both underdosing and overdosing are possible -  if you're unsure, start at the lower end of the range and build from there.

Frequently asked questions

Can I just follow 20 minutes five times a week and get results?
You might, but you might not -  and you won't know which without understanding your actual dose. Minutes alone aren't the dose. mW/cm² multiplied by time (in seconds) divided by 1000 gives you J/cm², which is the actual measure of energy delivered. Some people following generic "20 minute" advice are underdosing significantly because they're standing too far away. Others are overdosing because they're close to a high-power panel and running long sessions. Both give suboptimal results. Once you know your panel's irradiance at your working distance, you can dial this in quickly.

Does red light therapy actually work for muscle recovery and DOMS?
The evidence here is among the strongest in the photobiomodulation literature. Multiple meta-analyses show consistent reduction in DOMS and improvements in recovery when dosing is correct. The mechanism is well established: improved ATP production in muscle cells, reduced inflammatory cytokines, better local circulation. The important qualifier is "when dosing is correct" - which is why protocol matters more than just switching a panel on.

How do I know if I'm overdoing red light therapy?
Feeling unusually drowsy, flat, or drained directly after a session is the main signal. This is the inhibitory phase of the biphasic dose response,  too much light energy can switch the mitochondrial response from stimulation to suppression. The fix is simple: back off on time, move further from the panel, or reduce session frequency. You should feel more energised after a session, not less. If that's not happening, the dose needs to come down before anything else.

Hva er forskjellen på rødt lys og nær-infrarødt lys for trening?
Rødt lys (630–660 nm) penetrerer primært overfladisk vev,  hud, overfladiske muskler og bindevev nær huden. Nær-infrarødt (800–850 nm) går dypere og er mer effektivt for dypere muskler, ledd og tendoner. For muskelgjenoppretting etter hard trening vil du ha begge — rødt for overflateeffekten og stimulering av blodsirkulasjon, nær-infrarødt for de dypere strukturene. De fleste gode treningspaneler kombinerer begge bølgelengdene av akkurat denne grunn.

References

• Biphasic dose response / Arndt-Schulz curve: PubMed 22461763 | PMC3315174
• PBM and muscle performance / DOMS meta-analysis: PubMed 29090398
• 660 nm and 830 nm in skeletal muscle fatigue: PMC3282894
• Parameters and photobiomodulation efficacy (irradiance, fluence, area): PMC8355782