Blood Tests Before HRT: What to Check and Why

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 otherwise healthy 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.

One thing belongs up front, though, because it matters more than any blood test. Bleeding changes are common in perimenopause, but persistent or unusually heavy bleeding, bleeding after sex, or any bleeding after menopause should be assessed by a clinician rather than put down to hormones, whatever is decided about tests or HRT.

This article explains what NICE actually recommends, and which further tests can be useful when symptoms, bleeding pattern or medical history suggest another cause may be contributing. Brooksby Medical sells private blood tests, so it is worth saying plainly: none of the tests discussed here is a routine requirement before HRT. Testing should be guided by your symptoms, bleeding pattern, medical history and risk assessment, not by a fixed panel.

What NICE says about blood tests and menopause

NICE guideline NG23, first published in 2015 and most recently updated in April 2026, is clear: otherwise healthy women aged 45 and over with typical menopausal symptoms should be identified clinically, without laboratory tests [NICE NG23]. Perimenopause is identified by vasomotor symptoms with menstrual cycle changes. In women aged 45 and over who are not using hormonal contraception, menopause is identified clinically after 12 months without a period. In women using hormonal contraception, menstrual bleeding cannot always be used reliably to establish menopausal status. The guideline wording covers women, trans men and non-binary people registered female at birth. This article uses the word women for readability.

The guideline specifically advises against using oestradiol, AMH, inhibin, antral follicle count or ovarian volume to diagnose menopause in women over 45 [NICE NG23]. FSH fluctuates too much during perimenopause for a single measurement to be reliable. Ultrasound may still be appropriate for other reasons, such as investigating abnormal bleeding or pelvic symptoms.

There are two situations where NICE says an FSH test may be considered:

• Women aged 40 to 45 with menopausal symptoms and menstrual changes [NICE NG23].

• 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, and does not set a numerical cut-off [NICE NG23]. Current UK practice standards, published by the BMS with partner royal colleges in June 2026, use FSH above 25 IU/L as the biochemical criterion, with a repeat sample after 4 to 6 weeks when there is diagnostic uncertainty [BMS Practice Standards, 2026]. The 2024 international POI guideline takes the same approach [ESHRE, 2024]. FSH also fluctuates, and ovarian function in POI can vary over time, so results are read against the laboratory method and the clinical picture. They are harder to interpret in women using hormonal contraception, and pregnancy and other causes of absent periods need to be considered.

Importantly, NICE does not specify any mandatory blood tests before starting HRT. The guideline permits prescribing HRT based on clinical diagnosis alone. Any further testing is a clinical decision based on the individual picture, not a guideline requirement.

Why some women have blood tests before starting HRT

There can be good clinical reasons for blood testing before starting HRT, even though NICE does not require it for making the perimenopause diagnosis. Several common conditions produce symptoms that closely mimic menopause, including thyroid dysfunction, iron deficiency, vitamin D deficiency, and pre-diabetes. These conditions can contribute to fatigue, brain fog, low mood or poor concentration, though these symptoms are nonspecific.

Without checking for them, there is a risk of attributing symptoms to menopause when a separate, treatable condition is contributing. That said, these tests are not routine prerequisites for HRT. They earn their place when something in the history suggests them: unexplained or persistent fatigue, heavy bleeding, a personal or family history of thyroid disease or diabetes, or symptoms that do not fit the usual pattern.

The blood tests a clinician may consider, and why

Menopause hormone tests: FSH and oestradiol

NICE says hormone tests are not needed for diagnosis in women over 45, and they are not needed before starting HRT either. Routine oestradiol testing is also not recommended for adjusting treatment. There is no agreed oestradiol target for symptom control, and levels vary with the timing of the sample, the preparation used and the laboratory assay. In selected situations, such as persistent symptoms on transdermal HRT where poor absorption is suspected, a specialist may check a level, but the response to treatment is generally judged on symptoms, side effects and bleeding pattern rather than a number. LH is rarely useful in routine menopause assessment.

Thyroid function tests: usually TSH, with free T4 when indicated

When symptoms or history raise the possibility of thyroid disease, thyroid function testing is one of the more useful investigations. Thyroid dysfunction is common in women around the menopause and can cause several symptoms that overlap with it, including fatigue, weight change, brain fog, low mood, hair changes 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. TSH is usually the first test. Free T4 is added when TSH is abnormal, when a pituitary cause is suspected, or when someone is already taking thyroid replacement.

There is also a direct interaction between oral HRT and thyroid medication. Oral oestrogen increases thyroxine-binding globulin (TBG). In women taking levothyroxine, this can increase the dose needed to keep thyroid function in the target range [Arafah, NEJM, 2001]. Thyroid tests may need reviewing after oral HRT is started or changed. Transdermal oestrogen does not significantly affect TBG. That is one of several factors a prescriber weighs when choosing between oral and transdermal treatment for women taking levothyroxine, alongside clot risk, migraine, cardiovascular history and personal preference.

HbA1c: blood sugar and metabolic risk

Insulin resistance tends to rise around the menopause, though weight change, age, sleep and activity levels all contribute alongside falling oestrogen. An HbA1c checks for non-diabetic hyperglycaemia, often called pre-diabetes (42 to 47 mmol/mol), or type 2 diabetes (48 mmol/mol and above). A single result of 48 or above is in the diagnostic range, but someone without symptoms generally needs a confirmatory test and clinical assessment before a diagnosis is made. HbA1c can also be less reliable in some types of anaemia, with certain haemoglobin variants, or when red cell turnover is altered, and a clinician may choose a different test in those situations. It belongs to normal diabetes risk assessment rather than being an HRT requirement. 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.

Lipid profile: cholesterol and cardiovascular risk

Cardiovascular risk generally increases with age and around the menopause. Changes in lipid levels, blood pressure, body composition, glucose metabolism and lifestyle can all contribute. Our guide to the 2026 cholesterol guidelines explains the current targets. The lipid profile is one of several factors that can influence 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. Markedly raised triglycerides need medical assessment in their own right. They may also be one reason a prescriber favours transdermal rather than oral oestrogen. HRT itself is not a treatment for cardiovascular risk. NICE advises against offering it for the prevention of cardiovascular disease.

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 liver enzymes such as ALT or GGT may prompt a prescriber to consider transdermal preparations, which avoid this first-pass exposure, although the liver still handles oestrogen later in its metabolism. Abnormal liver results need interpreting and investigating in their own right, and do not, by themselves, determine the safest HRT route. Known or active liver disease may need specialist or condition-specific advice, which your prescriber can arrange.

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 iron deficient. Ferritin is usually the most useful marker, though it rises with inflammation, infection and liver disease, so results need interpreting in context. A 2025 clinical practice review published in the CMAJ supports considering iron deficiency, and iron replacement, when ferritin falls below 30 micrograms per litre in non-pregnant adults, higher than the 15 microgram threshold still used by some laboratories [Sholzberg M et al., CMAJ, 2025]. Cut-offs vary with the clinical context and the laboratory method. Some clinicians use higher ferritin targets in selected patients, but a target above 50 micrograms per litre is not a universal guideline requirement, and evidence that it improves nonspecific symptoms is limited. Heavy or unexpected bleeding should always be assessed in its own right rather than assumed to be perimenopausal.

Vitamin D deficiency is common among menopausal women. It can cause muscle aches and bone pain, and may sit alongside fatigue or low mood, but these symptoms are nonspecific [Mei Z et al., Frontiers in Physiology, 2023]. Testing is not routinely needed before HRT and is best reserved for women with risk factors or a clinical suspicion of deficiency. On supplements, UK government advice is a daily 10 microgram (400 IU) dose for most adults over autumn and winter, taken year-round by people at higher risk of deficiency [NHS]. Higher doses may be prescribed when deficiency is confirmed or when there are specific bone health or malabsorption risks, and should be clinician directed. Calcium supplements are not automatically needed alongside HRT. Diet, kidney stone history, kidney function and cardiovascular risk all come into that decision, which is best made with a clinician, and calcium is best obtained from food where possible.

When to have your blood tests: timing matters

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

• FSH is requested on days 2 to 5 of the cycle by some local protocols in women who are still cycling, although single measurements are unreliable during perimenopause. For suspected POI, the 2024 international guideline states that testing does not need to be timed to a particular cycle day [ESHRE, 2024].

• Lipid profile no longer routinely requires fasting. UK guidance accepts non-fasting samples for cholesterol testing [NICE, NG238], though a clinician may request a fasting sample if triglycerides are markedly raised.

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

• Hormonal contraception suppresses FSH, LH, and oestradiol, and NICE advises against using FSH to diagnose menopause in women using combined hormonal contraception or high-dose progestogen [NICE NG23]. Do not stop contraception just to get a blood test. Stopping risks pregnancy, and any pause should be planned with a clinician who can advise on alternative cover in the meantime.

• Biotin supplements can interfere with some laboratory immunoassays, including thyroid tests [Favresse et al., 2018]. Tell the clinician and laboratory about any biotin-containing supplement when you book. The right withholding period depends on the dose and the assay, often 48 to 72 hours, and prescribed high-dose biotin should not be stopped without medical advice.

  
  

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. Any service arranging private tests should also explain who reviews the results, how urgent abnormal results are communicated, and what follow-up is available. No one should be left to interpret an abnormal result alone. At Brooksby Medical, a GP reviews every result before it is released. This review does not replace a full clinical assessment, and we will say when GP or specialist follow-up is needed. You should see your GP if:

• You have persistent or worsening symptoms despite being on HRT.

• You have bleeding on HRT outside the expected settling-in period. Bleeding is common during the first 6 months of systemic HRT, or within 3 months of a change in dose or preparation, but bleeding beyond those windows, or bleeding that is heavy or worrying, needs assessment [NICE NG23].

• 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. Any concerning result should be discussed promptly with the clinician responsible for reviewing it, or with your GP.

References

1. NICE. Menopause: identification and management (NG23). Published 2015, last updated 15 April 2026. NICE guideline

2. BMS, RCOG and partner societies. Menopause Practice Standards, June 2026. British Menopause Society

3. ESHRE Guideline Group on POI. Evidence-based guideline: premature ovarian insufficiency. Hum Reprod Open. 2024;2024(4):hoae065. Human Reproduction Open

4. Arafah BM. Increased need for thyroxine in women with hypothyroidism during estrogen therapy. NEJM. 2001;344:1743-1749. doi: 10.1056/NEJM200105313442201

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

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

7. NHS. Vitamin D: vitamins and minerals. NHS

8. NICE. Cardiovascular disease: risk assessment and reduction, including lipid modification (NG238), 2023. NICE guideline

9. Favresse J, Burlacu MC, Maiter D, Gruson D. Interferences with thyroid function immunoassays: clinical implications and detection algorithm. Endocr Rev. 2018;39(5):830-850. Endocrine Reviews

Medically reviewed: August 2026 | Next review due: August 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.