How many hyperbaric oxygen therapy sessions do you actually need?
This is the question everyone asks second, right after "what does it do."
The answer you usually get is a number that matches whatever pack the person is selling. Ten is popular. Ten is a nice round number, it makes a tidy price, and it has almost nothing to do with the research.
Here is what the trials actually did.
The short answer
For a general sense of whether you like it: one session. You will know within an hour whether the experience suits you. That is all one session tells you, and it is worth knowing.
For anything the published research has measured: forty to sixty sessions, delivered five days a week over eight to twelve weeks. That is the protocol behind nearly every positive study in the wellness-adjacent hyperbaric literature. It is a serious commitment of time and money and almost nobody discloses it up front.
For "ten sessions and you're sorted": no evidence. The largest, best-blinded trial that used ten sessions found no benefit over placebo [1].
Everything below is the detail behind those three lines.
What the actual studies did
Let us go through the research that gets quoted in hyperbaric marketing and look at the session counts, because the session count is usually the part that gets left out.
Cognitive function in healthy older adults: 60 sessions
The trial people mean when they say "hyperbaric improves brain function in ageing" randomised 63 healthy adults aged 64 and over. The protocol was 60 daily sessions over 90 days, five days a week, 90 minutes each, at 2.0 ATA. It found improved global cognitive function against controls, with the largest effects in attention and processing speed, and increased cerebral blood flow [2].
Sixty sessions. Ninety minutes each. Ninety days. That is 90 hours in a chamber.
Telomere length and cellular ageing: 60 sessions
The study that launched a thousand Instagram posts about hyperbaric oxygen "reversing ageing" enrolled 35 adults over 64 and analysed 30. Protocol: 60 daily sessions, five days a week, 90 minutes at 2.0 ATA. It reported increased telomere length in isolated blood cells and a reduction in senescent T-helper cells [3].
Two things about this study that rarely survive the trip to social media. It had no control group, and n was 30. It is a legitimate, peer-reviewed, interesting result, and it is a single-arm trial in thirty people. It is not proof of anything, and it certainly is not proof about session five.
Fibromyalgia: 40 sessions
A crossover trial of 60 women used 40 sessions over two months, five days a week, 90 minutes at 2.0 ATA. It found significant improvement in symptoms and quality of life with corresponding changes on brain imaging [4]. A later randomised trial in a specific subgroup used 60 sessions [5].
The meta-analytic picture here is genuinely mixed, incidentally. One systematic review of nine studies found improvements in pain, fatigue, function and sleep [6]. Another, restricted to four randomised trials, found improvement in function but no significant reduction in pain, plus significantly more adverse events [7]. Both are real. They disagree.
Post-COVID cognitive symptoms: 40 sessions versus 10 sessions
This is the most instructive comparison in the entire literature, and it is worth sitting with.
Forty sessions. A sham-controlled randomised trial of 73 people ran 40 daily sessions at 2.0 ATA and found improvements in global cognitive function, attention and executive function, with matching changes in brain perfusion [8].
Ten sessions. A separate randomised, placebo-controlled, double-blind trial of 79 people ran 10 sessions and found no benefit over placebo in the short term. Both groups improved [1].
Same condition. Different dose. Opposite result.
And to keep it honest, a 2024 living systematic review of long COVID interventions published in the BMJ, covering 24 trials, found no compelling evidence supporting hyperbaric oxygen at all, while favouring rehabilitation and cognitive behavioural therapy [9]. The field has not settled this.
The pattern
Line them up:
Cognition, adults 64+ — 60 sessions, 2.0 ATA — Positive [2]
Telomeres, adults 64+ — 60 sessions, 2.0 ATA — Positive, uncontrolled [3]
Fibromyalgia — 40 sessions, 2.0 ATA — Positive [4]
Post-COVID cognition — 40 sessions, 2.0 ATA — Positive [8]
Post-COVID symptoms — 10 sessions, 2.0 ATA — No benefit over placebo [1]
Forty is the floor in the positive studies. Ten is where it failed.
There is also mechanistic evidence that this is cumulative rather than acute. A single 2.0 ATA exposure roughly doubles circulating CD34+ stem and progenitor cells. Twenty treatments raise them about eightfold [10]. The effect builds across a course. It is not a thing that happens in one hour.
Why "ten sessions" persists anyway
Three reasons, and only one of them is about you.
It is a sellable number. Ten sessions at a round price is a clean product. Forty sessions at any price is a mortgage.
It borrows from clinical protocols that are not comparable. Hospital hyperbaric courses often run 20 to 40 sessions for specific medical indications at higher pressures under supervision. "Around twenty or thirty" leaks into wellness marketing and gets trimmed to ten.
It is roughly where people stop. Ten is about the point at which the novelty of a daily chamber appointment collides with the rest of a life.
None of these are evidence.
What a session actually gives you
Worth separating three different things, because they have very different timelines.
The hour itself. Genuine and immediate. It is 60 minutes with no phone, no signal and nothing asked of you. Plenty of people book chamber time for exactly this and are entirely upfront about it. There is nothing wrong with buying an hour of enforced stillness. Just call it what it is.
How you feel that day. Variable and short-lived. Some people report clarity, some report tiredness. One randomised crossover study at mild pressure found a single exposure lowered resting heart rate and shifted heart rate variability, but did not improve aerobic performance [11]. Acute physiological changes are measurable. Acute performance changes are not.
Measured, durable change. This is the forty-to-sixty territory, and it is the only territory the positive research speaks to.
Conflating the first with the third is the fundamental dishonesty of hyperbaric marketing.
What the research says does not work, at any session count
Since we are being thorough: sports recovery.
A systematic review and meta-analysis found hyperbaric oxygen before exercise did not significantly improve performance, and after exercise did not significantly improve recovery [12]. A Cochrane review found insufficient evidence for delayed onset muscle soreness [13]. A 2026 systematic review of 19 clinical studies covering 612 patients reached the same conclusion for exercise-induced muscle damage, with randomised trials showing no significant benefit [14]. A 2026 meta-analysis did find reduced post-recovery blood lactate, but noted limited application to actual power output and force production [15].
If a provider is selling you a ten-pack for muscle soreness, more sessions will not fix that. The problem is not the dose.
So how should you approach it?
Start with one. Not as a taster leading to a pack, but as an actual test of whether you tolerate the pressure change, whether the chamber bothers you, and whether an hour in there is something you want in your week. A meaningful number of people find out they do not like it, and that is a completely reasonable outcome for one session.
If you want to keep going, think in blocks of ten, not in packs. Ten sessions over two to three weeks will tell you whether the rhythm fits your life. It will not tell you whether it is "working," because the research says ten does not do much. It tells you whether you can sustain the schedule, which is the actual constraint.
If you are chasing what the studies measured, commit properly or do not bother. Forty sessions, five days a week, eight weeks. Be honest about whether you will do that before you buy anything. Most people will not, and there is no shame in it, but half-committing to a 40-session protocol produces a 15-session protocol, and there is no evidence for that either.
And know what you are buying. Pressure is dose. A course at 1.3 ATA is not the same course as one at 2.0 ATA, and it is not what the studies above used. We have written about that separately: mild HBOT vs clinical HBOT and what the ATA number means.
What about side effects across a long course?
Fair question if you are considering forty sessions.
Across 2,334 patients and 62,614 sessions, roughly 17% of patients experienced at least one adverse event, and the overall seizure rate was 0.011%, about one in 8,945 sessions [16][17]. In two closely monitored trials covering 4,245 chamber sessions, adverse events occurred in 1.1% to 2.2% of sessions and were mostly minor ear barotrauma [18].
Middle ear barotrauma is the common one and it is a first-sessions problem more than a fortieth-session problem, since most people learn to clear their ears. Temporary short-sightedness is the one that specifically comes with long courses, and it reverses after treatment stops [19][20].
Our position
We are not going to sell you a number.
Sessions at our Byron Bay chamber are $49.99 until the end of 2026, single sessions, no pack, no membership required, no lock-in. That is deliberate. At that price you can test the thing honestly instead of committing to a protocol you have not decided you want.
Our chamber is a hard-shell unit running to 2.0 ATA, which is the pressure the studies above actually used. If you decide you want to run a real course, you can run it here at the dose the research used, for less than the price of a single session at most places.
If you already know you want ongoing access, our membership options are worth a look.
We are a wellness club, not a medical clinic. Our sessions are not intended to diagnose, treat, cure or prevent any disease or medical condition. If you have a health condition, talk to your doctor before booking.
References
1. Kjellberg A, et al. Ten sessions of hyperbaric oxygen versus sham treatment in patients with long covid (HOT-LoCO): randomised, placebo-controlled, double-blind, phase II trial. BMJ Open 2025;15(4):e094386. PMID 40228859. https://pubmed.ncbi.nlm.nih.gov/40228859/
2. Hadanny A, et al. Cognitive enhancement of healthy older adults using hyperbaric oxygen: a randomized controlled trial. Aging (Albany NY) 2020;12(13):13740-13761. PMID 32589613. https://pubmed.ncbi.nlm.nih.gov/32589613/
3. Hachmo Y, et al. Hyperbaric oxygen therapy increases telomere length and decreases immunosenescence in isolated blood cells: a prospective trial. Aging (Albany NY) 2020;12(22):22445-22456. PMID 33206062. https://pubmed.ncbi.nlm.nih.gov/33206062/
4. Efrati S, et al. Hyperbaric oxygen therapy can diminish fibromyalgia syndrome: prospective clinical trial. PLoS One 2015;10(5):e0127012. PMID 26010952. https://pubmed.ncbi.nlm.nih.gov/26010952/
5. Boussi-Gross R, et al. Hyperbaric oxygen therapy vs pharmacological intervention in fibromyalgia patients following childhood sexual abuse: randomized controlled trial. Scientific Reports 2024;14(1):11599. PMID 38773296. https://pubmed.ncbi.nlm.nih.gov/38773296/
6. Chen X, et al. Efficacy and safety of hyperbaric oxygen therapy for fibromyalgia: systematic review and meta-analysis. BMJ Open 2023;13(1):e062322. PMID 36690401. https://pubmed.ncbi.nlm.nih.gov/36690401/
7. Cao C, et al. Hyperbaric oxygen therapy for fibromyalgia: a meta-analysis of randomized controlled trials. Clinics and Practice 2023;13(3):583-595. PMID 37218804. https://pubmed.ncbi.nlm.nih.gov/37218804/
8. Zilberman-Itskovich S, et al. Hyperbaric oxygen therapy improves neurocognitive functions and symptoms of post-COVID condition: randomized controlled trial. Scientific Reports 2022;12(1):11252. PMID 35821512. https://pubmed.ncbi.nlm.nih.gov/35821512/
9. Zeraatkar D, et al. Interventions for the management of long covid: living systematic review and network meta-analysis. BMJ 2024;387:e081318. PMID 39603702. https://pubmed.ncbi.nlm.nih.gov/39603702/
10. Thom SR, et al. Stem cell mobilization by hyperbaric oxygen. American Journal of Physiology: Heart and Circulatory Physiology 2006;290(4):H1378-86. PMID 16299259. https://pubmed.ncbi.nlm.nih.gov/16299259/
11. Hu Z, Guo W, Wu H. Effects of acute mild hyperbaric oxygen exposure on cardiac autonomic function and aerobic performance. Journal of Physiological Anthropology 2025;44(1):22. PMID 40676637. https://pubmed.ncbi.nlm.nih.gov/40676637/
12. Huang X, et al. Effects of hyperbaric oxygen on exercise performance and recovery: systematic review and meta-analysis. Frontiers in Physiology 2021;12:791872. PMID 34887780. https://pubmed.ncbi.nlm.nih.gov/34887780/
13. Bennett M, Best TM, Babul S, Taunton J, Lepawsky M. Hyperbaric oxygen therapy for delayed onset muscle soreness and closed soft tissue injury. Cochrane Database of Systematic Reviews 2005;(4):CD004713. PMID 16235376. https://pubmed.ncbi.nlm.nih.gov/16235376/
14. Weinrich L, et al. Hyperbaric oxygen therapy in musculoskeletal medicine: a systematic review. BMC Musculoskeletal Disorders 2026;27(1):661. PMID 42576206. https://pubmed.ncbi.nlm.nih.gov/42576206/
15. Babel S, Bosco G, Camporesi E. Hyperbaric oxygen and exercise recovery: a meta-analysis. Undersea and Hyperbaric Medicine 2026;53(2):305-318. PMID 42365952. https://pubmed.ncbi.nlm.nih.gov/42365952/
16. Hadanny A, et al. Seizures during hyperbaric oxygen therapy: retrospective analysis of 62,614 treatment sessions. Undersea and Hyperbaric Medicine 2016;43(1):21-28. PMID 27000010. https://pubmed.ncbi.nlm.nih.gov/27000010/
17. Hadanny A, et al. Adverse events during hyperbaric oxygen therapy. Undersea and Hyperbaric Medicine 2016;43(2):113-122. PMID 27265988. https://pubmed.ncbi.nlm.nih.gov/27265988/
18. Churchill S, et al. Adverse events in hyperbaric oxygen and sham chamber sessions. Undersea and Hyperbaric Medicine 2019;46(3):331-340. PMID 31394602. https://pubmed.ncbi.nlm.nih.gov/31394602/
19. Heyboer M, et al. Hyperbaric oxygen therapy: side effects defined and quantified. Advances in Wound Care 2017;6(6):210-224. PMID 28616361. https://pubmed.ncbi.nlm.nih.gov/28616361/
20. Camporesi EM. Side effects of hyperbaric oxygen therapy. Undersea and Hyperbaric Medicine 2014;41(3):253-7. PMID 24984321. https://pubmed.ncbi.nlm.nih.gov/24984321/
