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Blood Tests Before HRT: What to Check and Why

  • Writer: Dr James Coleman
    Dr James Coleman
  • 6 days ago
  • 6 min read

If you are considering HRT, one of the first questions you will probably ask is whether you need blood tests beforehand. The answer depends on what the tests are for. Blood tests to diagnose menopause or perimenopause are rarely needed. Blood tests to exclude other causes of your symptoms are a different matter entirely. NICE guideline NG23 says most women aged 45 and over can be diagnosed with perimenopause or menopause on symptoms alone, without any laboratory tests at all. Many GPs follow this approach, and for straightforward cases it works well.


This article explains what NICE actually recommends, which additional tests specialist menopause clinicians request and why.


What NICE says about blood tests and menopause

NICE guideline NG23, updated in November 2024, is clear: women aged 45 and over with typical menopausal symptoms should be identified clinically, without laboratory tests [NICE, 2024]. Perimenopause is identified by vasomotor symptoms with menstrual cycle changes. Menopause is confirmed after 12 months without a period.

The guideline specifically advises against using oestradiol, AMH, inhibin, or ovarian ultrasound to diagnose menopause in women over 45 [NICE, 2024]. FSH fluctuates too much during perimenopause for a single measurement to be reliable.

There are two situations where FSH testing is recommended:

  • Women aged 40 to 44 with menopausal symptoms and menstrual changes [NICE, 2024]

  • Women under 40 where premature ovarian insufficiency (POI) is suspected. NICE recommends two FSH samples taken 4 to 6 weeks apart, with levels consistent with ovarian insufficiency. The BMS uses a threshold of above 40 IU/L on both occasions [BMS, 2024]

Importantly, NICE does not specify any mandatory blood tests before starting HRT. The guideline permits prescribing HRT based on clinical diagnosis alone. This is where specialist practice goes further than the minimum guideline requirement.


Why baseline blood tests matter before starting HRT

There are good clinical reasons for checking baseline bloods before starting HRT, even though NICE does not require it for making the peri-menopause diagnosis. Several common conditions produce symptoms that closely mimic menopause, including thyroid dysfunction, iron deficiency, vitamin D deficiency, and pre-diabetes. All of these cause fatigue, brain fog, low mood, and poor concentration.


Without checking for them first, there is a risk of attributing symptoms to menopause when a separate, treatable condition is contributing.


The blood tests worth having before HRT


Hormones: FSH, LH, and oestradiol

Even though NICE says hormone tests are not needed for diagnosis in women over 45, they still serve a purpose. A baseline FSH and oestradiol measurement gives your clinician a reference point. Once HRT is started, exogenous oestrogen suppresses FSH, so the pre-treatment value is the only one you will ever get. Low levels of oestradiol are typical in postmenopausal women. If symptoms persist on transdermal HRT, a repeat oestradiol level can help check whether the patch or gel is being absorbed properly.


Thyroid function: TSH and free T4

This is arguably the most important pre-HRT blood test. Thyroid dysfunction is common in women around the menopause, and the symptom overlap is almost complete: fatigue, weight gain, brain fog, low mood, hair thinning, and cold intolerance. An underactive thyroid is unlikely to resolve with HRT alone, so identifying it beforehand avoids months of dose adjustments that miss the real problem.

There is also a direct interaction between oral HRT and thyroid medication. Oral oestrogen increases thyroxine-binding globulin (TBG), which can reduce the amount of free thyroxine available in the blood [Arafah, NEJM, 2001]. Women taking levothyroxine who start oral HRT may need their dose reviewed. Transdermal oestrogen does not significantly affect TBG, which is one of the reasons it is generally preferred for women on thyroid replacement.


HbA1c: blood sugar and metabolic risk

Menopause increases insulin resistance as oestrogen declines. A baseline HbA1c screens for pre-diabetes (42 to 47 mmol/mol) or type 2 diabetes (48 mmol/mol and above). NICE NG23 notes that HRT does not increase the risk of developing type 2 diabetes and generally has no adverse effect on blood glucose control. Knowing your starting point means any future metabolic changes can be tracked.


Lipid profile: cholesterol and cardiovascular risk

Cardiovascular risk rises after menopause as oestrogen's protective effects on lipid metabolism diminish. The lipid profile directly influences HRT route selection. Oral oestrogen raises HDL cholesterol but can also raise triglycerides meaningfully in some women. Transdermal oestrogen has a more neutral triglyceride effect. If your fasting triglycerides are elevated, your prescriber may prefer transdermal HRT for this reason.


Liver function tests

Oral oestrogen undergoes first-pass hepatic metabolism (meaning it passes through the liver before reaching the rest of the body), which increases production of clotting factors, SHBG (sex hormone-binding globulin), and triglycerides. Elevated baseline liver enzymes such as ALT or GGT may point towards transdermal preparations, which bypass the liver entirely. If you have active liver disease, your prescriber will assess whether oral HRT is appropriate for you.


Full blood count, ferritin, and vitamin D

Heavy perimenopausal bleeding is common and depletes iron stores well before haemoglobin drops. A woman can have a completely normal full blood count and still be profoundly iron deficient. Ferritin is the most sensitive marker. A 2025 clinical practice review published in the CMAJ redefined the treatment threshold, recommending that iron replacement should be considered when ferritin falls below 30 micrograms per litre in non-pregnant adults, significantly higher than the outdated 15 microgram threshold still used in some laboratories [Sholzberg M et al., CMAJ, 2025]. Many specialists target above 50 for optimal symptom relief.

Vitamin D deficiency is widespread among menopausal women and causes fatigue, muscle pain, and low mood, symptoms easily attributed to menopause rather than a correctable deficiency [Mei Z et al., Frontiers in Physiology, 2023]. The British Menopause Society recommends daily supplementation of 1,000 IU vitamin D alongside 1,000 mg calcium for bone health.



When to have your blood tests: timing matters

Getting the timing right makes a genuine difference to the accuracy of your results.

  • FSH and LH are best tested on days 2 to 5 of the menstrual cycle in cycling women, though single measurements are unreliable during perimenopause

  • Lipid profile requires 8 to 12 hours fasting. Triglycerides are significantly elevated after eating

  • HbA1c, ferritin, vitamin D, and thyroid tests do not require fasting

  • Hormonal contraception suppresses FSH, LH, and oestradiol. For accurate hormone assessment, stop hormonal contraceptives for a minimum of 14 days, ideally waiting 3 full menstrual cycles

  • Biotin supplements should be stopped at least 72 hours before thyroid testing as they can interfere with immunoassay accuracy


When to see your GP

Private blood testing can give you useful information, but it does not replace a face-to-face assessment by your GP or menopause specialist. You should see your GP if:

  • You have persistent or worsening symptoms despite being on HRT

  • Your blood results show significantly abnormal values, particularly in thyroid function, HbA1c, liver enzymes, or full blood count

  • You are experiencing symptoms that could indicate something other than menopause, such as unexplained weight loss, persistent palpitations, rectal bleeding, or severe mood disturbance

  • You are considering testosterone therapy and want to discuss whether it is appropriate for your situation

  • You have a personal or family history of breast cancer, cardiovascular disease, or VTE and are unsure whether HRT is safe for you

Your GP has access to your full medical history and can arrange further investigations, referrals, or prescriptions that a private blood test alone cannot provide. If any result concerns you, your next step should always be a conversation with your doctor.


How Brooksby Medical can help

At Brooksby Medical, every blood test report is written by a practising GP who contextualises your results together, not just flags individual markers as high or low. That clinical interpretation is particularly important with hormone results, where the interaction between oestradiol, FSH, thyroid function, SHBG, and testosterone levels matters more than any single number.

If you are considering HRT or want a comprehensive baseline before your next GP or menopause clinic appointment, the following tests may be relevant:

All tests are available as a home fingerprick kit, at a partner phlebotomy clinic near you, or with a home phlebotomist visit. Results are returned within 2 to 3 working days with a GP-written report.


References

  1. NICE. Menopause: identification and management (NG23), updated November 2024. NICE guideline

  2. BMS. Statement in response to the updated NICE Menopause guideline, November 2024. British Menopause Society

  3. Arafah BM. Increased need for thyroxine in women with hypothyroidism during estrogen therapy. NEJM. 2001;344:1743-1749

  4. Mei Z, Hu H, Zou Y, Li D. The role of vitamin D in menopausal women's health. Front Physiol. 2023;14:1211896

  5. Sholzberg M, Hillis C, Crowther M, Selby R. Diagnosis and management of iron deficiency in females. CMAJ. 2025 Jul 2;197(24):E680–E687. doi: 10.1503/cmaj.240570 CMAJ. 2025

Medically reviewed: March 2026 | Next review due: March 2027

Written by Dr James Coleman, GP and founder of Brooksby Medical. Dr Coleman is a practising General Practitioner who founded Brooksby Medical to give patients direct access to the blood tests and clinical interpretation they need, without waiting lists.

Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Blood test results should always be interpreted by a qualified healthcare professional in the context of your individual symptoms, medical history, and clinical picture. If you have concerns about your health, please consult your GP.

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