Women's hormones
Hot Flushes: What They Mean and When to Test
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Last reviewed July 20267 min read
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Most hot flushes come from the menopause transition, when falling oestrogen unsettles the body's temperature control. If you are 45 or over, UK guidance says you do not need a blood test to confirm it. Under 45, or if the pattern is unusual, testing helps rule out thyroid and other causes.
A wave of heat rises through your chest and face. You flush, you sweat, your heart races for a minute, then it passes. It happens in meetings, in bed, in the supermarket queue. For most women in midlife, this is the first clear sign that the menopause transition has begun.
Hot flushes are common, but they are not always about hormones. This guide explains what causes them, when a blood test genuinely helps, and the other conditions worth ruling out before you assume it is menopause.
By Helvy Medical Team · 7 min read
1. What causes hot flushes?
The common cause is the menopause transition. As oestrogen falls, the brain's thermostat, sitting in a region called the hypothalamus, becomes more sensitive. A tiny rise in body temperature is read as too hot, so the body reacts by widening blood vessels and sweating to cool you down. That reaction is the flush.
The NHS describes a hot flush as a sudden feeling of heat in the face, neck and chest, often with sweating, a racing heart or a moment of anxiety. When it wakes you at night, it is called a night sweat, which our night sweats guide covers in detail.
They are also very common. Around three in four women get hot flushes around menopause. And they can last longer than people expect. In the large SWAN study, the median total duration of hot flushes and night sweats was 7.4 years, so this is rarely a matter of a few months.
2. Do you need a blood test to confirm menopause?
If you are 45 or over, usually not. UK guidance is clear on this point, and it surprises many women.
“Women… aged 45 or over presenting with menopause associated symptoms are diagnosed with perimenopause or menopause based on their symptoms alone, without confirmatory laboratory tests.”
— NICE Quality standard QS143, Menopause (2017)
The reason is simple. During the perimenopause, hormone levels swing from day to day, so a single blood test can read normal even when the transition is well underway. Symptoms tell the story more reliably than one snapshot.
Under 45, the picture changes. Here a blood test does earn its place, because early menopause and other causes need to be checked. Our early menopause guide explains when testing FSH matters and what the results mean.
3. When hot flushes are not just menopause
Menopause is the usual answer, but it is not the only one. The most important look-alike is an overactive thyroid. It can cause the same heat, sweating and palpitations, plus weight loss, shaky hands and a racing pulse. It is easy to miss when everyone assumes hormones.
Other triggers worth knowing about include:
- Anxiety and panic, which can flush the skin and race the heart
- Alcohol, caffeine, spicy food and a hot room
- Some medicines, including certain antidepressants and painkillers
- Low blood sugar in people managing diabetes
This is where a blood test helps most. It does not confirm menopause in an over-45 woman, but it can rule the other causes in or out. Checking thyroid function alongside your hormones is the practical way to tell them apart, and our thyroid blood test guide explains what the markers show.
4. How is it tested properly?
When testing is the right step, one hormone is not enough. A useful panel reads a few markers together:
- FSH and LH, the pituitary hormones that rise as the ovaries wind down
- Thyroid (TSH), to check an overactive thyroid is not behind the heat
- SHBG and testosterone, which round out the hormone picture as your cycle changes
Timing matters too. If you still have periods, an FSH result reads best in the first few days of your cycle. A morning sample is ideal. Our menopause blood test guide walks through the timing and what each result means.
Our Hormone Balance panel (£99) measures FSH, LH, SHBG, testosterone and the free androgen index from one morning finger-prick sample, with every marker explained in plain English. Add a thyroid check if flushing with weight loss or a racing pulse is part of your picture.
5. What can help hot flushes?
Small changes ease flushes for many women. The NHS suggests keeping the room cool, dressing in light layers, and cutting back on common triggers such as caffeine, alcohol, spicy food and smoking. Regular exercise and steady stress management help too.
When flushes disrupt daily life, the NHS describes hormone replacement therapy (HRT) as the main treatment for menopausal symptoms. Whether it suits you is a conversation for your GP or a menopause specialist, based on your history and preferences. A clear picture of your hormones and thyroid is a good place to start that conversation.
CHECK YOUR HORMONES
The Hormone Balance panel (£99) reads FSH, LH, SHBG, testosterone and the free androgen index from a simple home sample, with a clear explanation of every result. Build the test that fits you in two minutes.
6. Frequently asked questions
Do hot flushes always mean menopause?
No. Menopause is the common cause in midlife, but an overactive thyroid, anxiety, some medicines and lifestyle triggers can cause the same heat and sweating. If the pattern seems unusual or comes with weight loss and a racing pulse, it is worth checking further.
How long do menopause hot flushes last?
Longer than most people expect. In the SWAN study, the median total duration was 7.4 years, and some women have them for a decade or more. Each individual flush usually passes within a few minutes.
Can a blood test tell me if I'm in menopause?
If you are 45 or over, UK guidance says menopause is diagnosed from your symptoms alone, because hormone levels swing too much for one test to be reliable. Under 45, an FSH test does help, and it can also rule out other causes at any age.
Can thyroid problems cause hot flushes?
Yes. An overactive thyroid speeds the body up and can cause heat, sweating, palpitations and weight loss that look like menopause. A simple thyroid check, read alongside your hormones, is the way to tell them apart.
At what age do hot flushes usually start?
Most women notice them in their late 40s to early 50s, often before periods stop, during the perimenopause. Starting much earlier can point to early menopause, which is worth investigating with a blood test. Our perimenopause guide explains the early signs.
Medical disclaimer: This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Guidance and thresholds cited here are based on NICE, NHS and published research, and may differ from the ranges used by your local laboratory. Do not start, stop or change medication, HRT, supplementation or treatment based solely on information in this article; consult your GP or a qualified healthcare professional. All Helvy blood tests are processed by UKAS-accredited UK laboratories to ISO 15189.
Last updated: July 2026 · By Helvy Medical Team · Analysed at UKAS-accredited UK laboratories
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