Hot Tub Health Benefits & Hydrotherapy: What the Evidence Shows
A warm soak has its strongest evidence for sleep.
Research suggests warm water before bed helps people fall asleep faster, and that gentle movement in warm water can ease stiff joints. Below, each benefit sits on a step, placed by how strong its evidence is.
Hot tub health benefits, from early research to strongest evidence
Read left to right. Each step up is stronger evidence.
The studies behind these steps used warm baths, showers, spa therapy and pool-based exercise. A hot tub gives you warm, supportive water at home.
Soothing arthritis with a warm soak
Nine trials with 579 people have looked at spa-style soaking for rheumatoid arthritis. The research is at an early stage, so it is best treated as a comfort.1
Cochrane review of 9 trialsEasing stiffness with gentle movement in water
Water-based exercise probably improves pain and disability slightly in knee and hip osteoarthritis,2 and eases stiffness in fibromyalgia.3
Cochrane reviews of 13 trials and 16 trialsFalling asleep faster
A review pooling 17 studies found that warm water 1 to 2 hours before bed shortened the time people took to fall asleep.4
Systematic review and meta-analysisWarm water before bed helps you fall asleep faster
A review that pooled 17 studies found that a warm bath or shower 1 to 2 hours before bed shortened the time it took to fall asleep, and people rated their sleep quality and efficiency higher too.4
The reason is simple. Warm water sends blood to your hands and feet, so afterwards your body loses heat faster, and a cooling body is part of how you drift off.4 The NHS also suggests relaxing for at least an hour before bed, with a bath or a book.5
A hot tub tops out at 40°C.6 Set yours to a temperature that feels good, never above that, and finish your soak an hour or two before you go to bed. Our hot tub temperature guide covers the settings.
Gentle movement in warm water eases stiff joints
Cochrane reviews of water-based exercise found that, for people with knee and hip osteoarthritis, a course of aquatic exercise probably improves pain and disability slightly and may improve quality of life slightly, with no serious side effects reported.2 For fibromyalgia, the evidence points to better wellness, less stiffness and improved fitness.3 The NHS lists swimming among the low-impact activities that suit arthritis.7
In the NHS, hydrotherapy means a physiotherapy programme in a warm pool, heated to 32–35°C and designed by a qualified physiotherapist. Warmth helps muscles relax and buoyancy supports your weight.8 A hot tub soak is one you run yourself, and it shares that warm, supportive water. Ask your GP or physiotherapist how it fits with your own plan.
Warm soaking and arthritis
Spa-style soaking for rheumatoid arthritis has been tested in nine trials with 579 people. The evidence so far is graded very low quality, and research is continuing.1 Many people simply find a warm soak comfortable and calming. If you have arthritis, your GP or specialist can say how it fits alongside your treatment.
Using your hot tub well
Most people settle between 36°C and 38°C, and the maximum is 40°C.6 If you are pregnant, have a health condition or take regular medication, speak to your GP before you use a hot tub. Our hot tub safety guide has the everyday checks.
If you are choosing a tub for evening soaks, you can compare seating layouts and sizes across our hot tubs collection.
Quick answers
Open a question to read the answer.
Do hot tubs have health benefits?
Research suggests a warm soak can help you fall asleep faster when you take it 1 to 2 hours before bed, and gentle movement in warm water can ease stiff joints. Other benefits are still being studied, so a hot tub is best seen as a way to relax and unwind.
Is a hot tub good for sleep?
A review of 17 studies found that warm water 1 to 2 hours before bed helped people fall asleep faster. Finish your soak an hour or two before bedtime and keep the water at or below 40°C.
Can a hot tub help with arthritis?
Reviews of water-based exercise found slight improvements in pain and disability for knee and hip osteoarthritis, and less stiffness in fibromyalgia. Soaking for rheumatoid arthritis is at an early stage of research, so talk to your GP or specialist about how it fits with your treatment.
What is hydrotherapy?
Hydrotherapy means using the properties of water, such as warmth and buoyancy, to ease the body. In the NHS it is a physiotherapy programme in a warm pool, and at home a hot tub gives you a warm water soak.
How hot should the water be?
Most people settle between 36°C and 38°C. The maximum for a hot tub is 40°C.
Who should speak to a GP before using a hot tub?
Anyone who is pregnant, has a health condition or takes regular medication. Your GP can say what suits you.
Sources
- Cochrane, Balneotherapy (or spa therapy) for rheumatoid arthritis, Verhagen et al., 11 April 2015
- Cochrane, Aquatic exercise for the treatment of knee and hip osteoarthritis, Bartels et al., 26 March 2016
- Cochrane, Aquatic exercise training for fibromyalgia, Bidonde et al., first published 28 October 2014
- Sleep Medicine Reviews, volume 46, Before-bedtime passive body heating by warm shower or bath to improve sleep, Haghayegh et al., August 2019
- NHS, Insomnia, last reviewed 19 March 2024
- BISHTA hot tub safety alert, via EuroSpaPoolNews, 13 June 2019
- NHS, Arthritis, last reviewed 19 January 2026
- Frimley Health NHS Foundation Trust, Hydrotherapy and aquatic therapy, last reviewed 28 January 2025
Paul Margerison
Managing Director & Founder, Outdoor Living
Better sleep and easier movement are good reasons to enjoy your hot tub. This guide sets out what the research says so you can soak with confidence.