Red Light Therapy for Blood Circulation: Scientific Evidence

Doses from 2.4 to 39.5 J/cm² were compared in a 2017 clinical trial testing laser light on blood drawn from 41 healthy volunteers aged 21 to 45. Red light at 662 nm was shone on the samples at 50 to 53 mW/cm² from about 5.91 inches, and the blood was then challenged with 3 different triggers of clumping. According to the trial, every dose reduced clumping to a meaningful degree, with the strongest effect at 19.7 J/cm². The work was carried out on blood samples rather than by treating the volunteers themselves.

Across 15 wavelengths spanning 400 to 940 nm, a 2016 observational study measured what happened to oxygen carried in the blood of the fingertip. A sensor clipped to the finger tracked oxygen levels while light-emitting diodes shone on the skin. Oxygen readings in the blood fell by about 5% under the light, with the effect strongest at 530, 600 and 850 nm. The study found this drop reflects oxygen being released from the blood into the surrounding tissue, which may be useful where tissue is short of oxygen.

In 2015, an observational study drew on more than 25 years of experience with laser light delivered into a vein to prevent blood vessel disease. Red light at 630 to 640 nm was used at 16 to 50 mW, in sessions of 1 to 30 minutes given across 5 to 21 days. Clotting cells clumped together up to 67% less and red cells up to 17% less in the patients described. The author concluded that this waveband acts on every type of cell in the blood, on the clotting process, and on the vessel wall itself, though the report presents accumulated experience rather than a controlled comparison.

A single-blind design compared real and dummy treatment in a 2013 randomized controlled trial measuring a molecule that helps blood vessels relax and widen. 15 healthy volunteers had a forearm treated with near-infrared light at 890 nm and 636 mW for 30 minutes, with blood drawn from the vein leaving the treated area before treatment, at 1, 5, 15, and 30 minutes, and 15 minutes afterward. Levels appeared to rise meaningfully, peaking 5 minutes into the session and easing back slowly after that. The researchers noted the volunteers were healthy, so the same rise cannot be assumed in people who are ill.

30 healthy volunteers took part in a 2012 randomized controlled trial comparing near-infrared light against a dummy device and against warm packs on the feet. The light came from an array of 60 diodes at 890 nm, each 12 mW, held against the skin for 30 minutes and delivering 60 mW/cm² and 108 J/cm² across 22.5 cm². According to the trial, blood cells moved faster through the smallest vessels and surface blood flow rose more in the group given real light than in either of the other 2 groups.

Published in 2000, this observational study used scans to see whether laser light changed blood flow in the skin of the foot. 6 healthy volunteers, 4 men and 2 women, had the sole of the right foot treated with near-infrared light at 780 nm, delivering 5 J/cm² at 100 mW/cm². Scans taken before and after showed a rise in the signal that tracks blood reaching the area, averaging 0.35 and ranging from 0.23 to 0.63 across the group. The researchers suggested this extra blood flow may be what lies behind the faster wound healing and reduced pain reported with such treatment.

Blood moved 2.31% faster through the surgically made vessel connection used for dialysis in patients under 65, in a 2025 observational study of 20 people on regular dialysis. Near-infrared light between 820 and 840 nm was shone on the palm for 20 minutes at 30 mW and 10 Hz, delivering 126 J and 73.16 J/cm². The gain kept building for at least 10 minutes after the light stopped, reaching 3.16% for speed and 1.59% for volume in the under-65 group. The study found age and how long someone had been on dialysis were the 2 things that decided who benefited, with older and longer-treated patients gaining less.

When 25 healthy adults were followed for around 6 months on a commercial wellness program, a 2024 observational study tracked what happened to their blood markers. Light therapy using red light between 620 and 780 nm was 1 of 7 treatments, running alongside whole-body cold exposure, infrared sauna, compression, mild hyperbaric oxygen and micronutrients given by drip and by injection, with participants also advised on exercise, diet and alcohol. Sessions averaged 40.31 of light therapy per person across roughly 214 days, though only 16 of the 25 had their session counts recorded. Among the 15 who returned for a second blood test, the cholesterol that raises risk fell by an average of 9.77 mg/dL and a marker of inflammation by 1.75 mg/L, while a blood sugar marker rose slightly and 3 other measures did not shift. No adverse events were reported, and because the treatments and the lifestyle advice ran together, the authors could not separate out what the light contributed.

10 of 20 healthy volunteers responded at all in a 2020 randomized controlled trial comparing red light at 633 nm against near-infrared light at 830 nm on the wrist. Each 5-minute session delivered 55 to 70 mW/cm² and 16.5 to 21 J/cm², with blood flow and skin temperature tracked during treatment and for 20 minutes afterward. The trial found near-infrared light raised flow in the smallest vessels by 27%, rising to 54% over the follow-up, while red light moved the median flow not at all. Whether someone responded came down to how warm their hands already were, with responders starting between 33 and 37.5 °C and non-responders either warmer or colder than that.

Comparing 30 people given laser treatment against 10 who were not, a 2016 clinical trial looked at how light affects the lining of blood vessels. The 40 volunteers were aged 20 to 40, and the treated group had near-infrared light at 808 nm and 50 mW aimed at the wrist artery from about 7.87 inches away, once a day for 3 consecutive days, delivering 20 J each day and 60 J in total. A natural antioxidant in the blood appeared to rise, and a protein that holds back new vessel growth appeared to fall in the treated group. 4 other markers, including those tied to the vessel-widening pathway, showed no meaningful change.

No improvement in blood vessel function followed treatment in a 2023 randomized controlled trial of 22 healthy volunteers, 77.3% of them women, at an average age of 25.45 years. Near-infrared light at 810 nm and 1 W was applied over the wrist and forearm arteries in a crossover design where neither the volunteers, the people giving the treatment nor the assessors knew which condition was which. 2 doses were tested, delivering 30 and 60 J at 107 and 214 J/cm², each on a single day.

Among 16 postmenopausal women aged 50 to 70, a 2022 randomized controlled trial tested whether LED light changes how the circulation recovers from a hard interval workout. Each woman completed 2 sessions 14 days apart, 1 with light and 1 with a placebo, receiving 940 nm light at 140 mW and 4.6 J/cm² for 102 seconds over the thigh and calf muscles. The trial found no difference between the light and placebo sessions in blood pressure after exercise. Measures of heartbeat variation and of a saliva marker linked to vessel widening also showed no advantage for the light.

Whether a single laser session changes blood flow or oxygen levels in the skin straight away was tested in a 2013 clinical trial on healthy volunteers. Red light at 660 nm and 350 mW was applied to the arch of 1 foot for 15 minutes at 5.73 J/cm², while a placebo treatment was given to the matching spot on the other foot, with neither the volunteers nor the assessors knowing which was which. The trial found no meaningful immediate change in either blood flow or oxygen levels. The researchers concluded that no instant effect should be expected when circulation starts out normal, and suggested repeating the work at different doses or in people with damaged tissue.