Exercise With Hashimoto's or an Underactive Thyroid When You're Exhausted

Exercise with Hashimoto's or an underactive thyroid can feel much harder than it used to, and that is a recognised effect, not a lack of willpower. Research shows reduced exercise tolerance is common, and for some people it does not fully return even when their thyroid results are in range. Small trials suggest gentle-to-moderate, regular activity can help people feel and function better. The key is to start small, build slowly, and stop pushing if activity leaves you worse for days.

If you used to run, lift or practise yoga every day and now a short walk wipes you out, this guide explains what is known, what tends to help, and the signs that mean you should stop and get checked.

Why exercise can feel so hard

A 2014 review of 38 studies found that reduced exercise tolerance is common with an underactive thyroid, both overt and mild. The researchers found that for some people it does not fully come back even once their thyroid results are in range, and said nobody yet knows why. They called it a forgotten area of research.

Other studies help explain what people feel:

• Muscles. Muscle aches and weakness are common when an underactive thyroid is first found. Most improve with treatment, but in one study about 1 in 8 people still had some weakness a year later.
• Heart rate. In one small study, the heart took longer to catch up at the start of exercise in people with a mildly underactive thyroid, and that slower start went with exercise feeling harder.
• After thyroid cancer. In a Canadian study, about 4 in 10 people treated for thyroid cancer had moderate to severe fatigue years later.

So if your results look fine and exercise still feels like wading through mud, that matches what research describes. It is worth raising with your GP rather than putting down to being unfit.

Does exercise help?

There are only small trials, but they point the same way:

• In a 12-week trial of people on levothyroxine, three gentle-to-moderate sessions a week, whether walking-style cardio, light resistance work or both, improved fitness and quality-of-life scores compared with no exercise.
• In a six-month trial, people on levothyroxine who did guided online yoga reported more energy and better quality of life than people on a waitlist.
• A 16-week aerobic program improved quality of life in people with a mildly underactive thyroid.

Reviews of yoga for an underactive thyroid find mostly positive results but small, lower-quality studies, so it is a reasonable gentle option, not a proven treatment. None of these trials shows that exercise replaces medication or fixes thyroid function. The honest summary is that regular, manageable movement can help you feel and function better, alongside your treatment.

How to start when you are exhausted

Australia's 24-Hour Movement Guidelines suggest about 30 minutes of moderate activity on most days and muscle-strengthening on two or more days a week. They also say that if you are not there yet, even small steps towards that can still improve your health, and to start slowly and build up. healthdirect puts it simply: doing some exercise is better than none.

• Start smaller than you think. A 10-minute walk, gentle stretching or a short yoga session counts.
• Build slowly. Add a few minutes at a time, and only when the current amount feels comfortable.
• Add some strength work. Simple bodyweight or light resistance exercises twice a week help keep muscles working. healthdirect has a beginner's guide.
• Choose gentler options on bad days. A slow walk or stretching still counts.
• Notice the next day, not just the moment. How you feel 24 hours later is a better guide than how you feel during the session.

Do not push through a crash

If activity reliably leaves you much worse for a day or more, that is a reason to see your GP and pace yourself, not to train harder. This pattern is sometimes called post-exertional fatigue. For ME/CFS, a different condition, the UK's NICE guidance recommends against graded exercise programs that keep increasing activity on a fixed schedule, and healthdirect recommends pacing instead. Your GP can look for other causes of exhaustion, such as low iron, sleep problems or a thyroid dose that needs another look.

Signs to stop and get checked

• Call 000 if you have palpitations with shortness of breath, chest pain, dizziness or fainting, or chest pain that is severe, getting worse or has lasted longer than 10 minutes.
• Fainting during or after exercise always needs to be checked by a doctor, even if you feel fine afterwards.
• A racing or pounding heart during light activity. On levothyroxine, this can be a sign the dose is too high. Ask your GP to check your thyroid tests, and do not change your dose yourself.
• An exercise injury that causes dizziness, weakness or severe pain needs prompt medical attention.

Exercise and your medication

There is no good evidence that the timing of exercise interferes with levothyroxine. One small study saw TSH shift when people started walking straight after their tablet, so if your routine changes a lot, mention it at your next thyroid test.

If you work out in the morning, your usual 30 to 60 minute gap before food still applies, and a protein shake counts as food. Anything with added calcium or iron needs a longer gap, usually around four hours. Check the label and ask your pharmacist. Our guide to protein powder and levothyroxine explains the timing.

Getting support in Australia

An accredited exercise physiologist is a university-qualified allied health professional who designs exercise programs for people with chronic conditions. If you have a long-term condition, your GP may be able to prepare a chronic condition management plan, which can give you Medicare benefits for up to five allied health services a year, including exercise physiology. Ask your GP whether you are eligible. You can find an accredited exercise physiologist through Exercise & Sports Science Australia.

Questions to ask your doctor

1. Could my thyroid dose be part of why exercise feels so hard?
2. Should we check anything else, such as iron, B12 or my sleep?
3. Is it safe for me to build up my activity, and how fast?
4. Am I eligible for a chronic condition management plan and sessions with an exercise physiologist?
5. What symptoms during exercise should make me stop and call you?

Where ThyroBase fits

No nutrition product replaces medical care, rest or a sensible exercise plan. ThyroBase is a daily morning and evening nutrition powder for people living with Hashimoto's, an underactive thyroid or no thyroid, designed to sit alongside your thyroid medication, never instead of it. Here is who ThyroBase is, and is not, designed for. If tiredness is your main struggle, our guide to still feeling tired with a normal TSH goes further.

Exercise feeling harder is a recognised effect, not a lack of willpower.

Start small, build slowly, and let how you feel tomorrow guide you.

Frequently asked questions

Why is exercise so hard with an underactive thyroid?

Reduced exercise tolerance is common with an underactive thyroid, and muscle weakness and a slower heart-rate response have both been described. For some people it does not fully return even when their thyroid results are in range, and the reasons are not yet understood. Talk to your GP if exercise feels much harder than it should.

Can exercise help Hashimoto's or an underactive thyroid?

Small trials suggest regular, gentle-to-moderate exercise and yoga can improve fitness, energy and quality of life in people with an underactive thyroid. None shows that exercise replaces medication or fixes thyroid function. It works best as part of your overall care.

How much exercise should I do if I am exhausted?

Start smaller than you think, such as a 10-minute walk or gentle stretching, and build up slowly. Australia's movement guidelines say even small steps help. If activity leaves you much worse for a day or more, ease off and talk to your GP rather than pushing through.

Is it normal to feel faint after exercising with a thyroid condition?

No. Fainting during or after exercise always needs to be checked by a doctor. Call 000 if fainting comes with chest pain, palpitations or shortness of breath. On levothyroxine, a racing heart during light activity can also mean your dose needs checking.

The honest takeaway

If exercise feels harder with a thyroid condition, research says you are not imagining it. Small trials suggest regular, manageable movement can help you feel and function better, so start small, build slowly, and include some strength work when you can. Rest when activity leaves you worse, take warning signs seriously, and ask for help, from your GP and, if you are eligible, an exercise physiologist.

ThyroBase is a nutritional supplement and is not intended to diagnose, treat, cure, or prevent any disease. It is designed to sit alongside your thyroid medication, not replace it. This article is general information, not medical advice. Check with your doctor before starting a new exercise program, and never start, stop or change a supplement or prescription medication without speaking to your doctor or pharmacist first.

References

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