HRT Monitoring Blood Test: Track Your Hormone Replacement Therapy

Approximately 1.5 million women in the UK are currently taking hormone replacement therapy (HRT) — a number that has risen sharply since the 2015 NICE guidelines clarified that the benefits of HRT outweigh the risks for most women under 60. But starting HRT is only half the equation. Monitoring your hormone levels on treatment is essential to ensure you're getting the right dose, through the right delivery route, with minimal side effects.

Both NICE and the British Menopause Society (BMS) recommend blood tests to confirm that hormone levels are therapeutic, especially for transdermal oestradiol (patches, gels, sprays), where absorption varies significantly between individuals.

The Key Markers for HRT Monitoring

Oestradiol — The Central Target

Oestradiol is the primary hormone you're replacing with HRT. Getting the level right determines whether your symptoms resolve and whether you're getting adequate bone and cardiovascular protection.

Optimal oestradiol ranges on HRT:

• Transdermal HRT (patches, gel, spray): target 200-600 pmol/L. Below 200 pmol/L suggests you need a dose increase — many women find symptoms only fully resolve above 300 pmol/L
• Oral HRT: oestradiol blood levels are less reliable because the liver metabolises oral oestrogen on first pass, converting much of it to oestrone (E1). A serum oestradiol level may look low on oral HRT even if the clinical effect is adequate

When to test: For patches, test at the trough — just before changing to a new patch (typically day 3 or 4 of a twice-weekly patch). For gel or spray, test before applying the morning dose. This gives you the lowest point in the dosing cycle, ensuring your trough level is adequate.

FSH — Confirming Adequate Replacement

FSH should decrease on adequate HRT — the exogenous oestrogen signals the pituitary to reduce FSH output. If FSH remains elevated above 30 IU/L despite HRT, it suggests the oestradiol dose is insufficient to suppress the hypothalamic-pituitary axis, and your prescriber should consider increasing the dose.

Conversely, very low FSH on HRT confirms that the dose is physiologically adequate — your body is "seeing" enough oestrogen to switch off the menopausal drive.

Progesterone

If you have a uterus and use micronised progesterone (Utrogestan) as part of your HRT, monitoring progesterone levels can confirm adequate endometrial protection. This is particularly relevant for women using vaginal progesterone or those with persistent bleeding on HRT. Target levels vary by route and timing but are worth discussing with your prescriber if breakthrough bleeding persists.

Testosterone

Testosterone prescribing for women in menopause is increasingly common, especially for low libido, fatigue, and brain fog that persist despite adequate oestrogen replacement. The BMS supports testosterone use in postmenopausal women with evidence of benefit.

• Female testosterone reference range: 0.3-1.7 nmol/L
• On testosterone cream/gel: aim for levels in the upper half of the female reference range
• Also check SHBG and free testosterone, as total testosterone alone can be misleading

SHBG (Sex Hormone-Binding Globulin)

SHBG is directly relevant to HRT monitoring because it's affected by the route of oestrogen delivery:

• Oral oestrogen raises SHBG (due to hepatic first-pass effect), which binds more testosterone and can worsen fatigue, low libido, and brain fog
• Transdermal oestrogen has minimal effect on SHBG, preserving free testosterone levels

If your SHBG is very high on oral HRT and you're experiencing persistent low-energy symptoms, switching to transdermal delivery may help — even at the same oestradiol dose.

Thyroid Function — The HRT Interaction

HRT increases thyroxine-binding globulin (TBG), which binds more thyroid hormone in the blood. For women with normal thyroid function, the body compensates automatically. But for women on thyroxine replacement for hypothyroidism, starting HRT can effectively reduce the available free thyroxine, potentially causing hypothyroid symptoms to return.

• If you take levothyroxine and start HRT: recheck TSH and FT4 at 6-8 weeks. You may need a thyroxine dose increase of 25-50 mcg
• Key markers: TSH, FT4, FT3

This interaction is particularly relevant for oral HRT (which raises TBG more than transdermal). If you're on both thyroxine and HRT and still feel fatigued, thyroid levels are the first thing to check.

Lipid Panel

The route of HRT delivery affects lipids differently:

• Oral oestrogen increases triglycerides — by up to 25% in some women. If you have pre-existing hypertriglyceridaemia, oral HRT is generally not recommended
• Transdermal oestrogen has no significant effect on triglycerides and may even improve the lipid profile
• Both routes tend to increase HDL and reduce LDL, which is cardiovascularly favourable

A baseline lipid panel before starting HRT, with follow-up at 6-12 months, helps ensure the treatment isn't worsening metabolic risk — particularly if you're on oral oestrogen.

Liver Function

Oral HRT is processed through the liver (first-pass metabolism), which makes liver function testing relevant for women on tablets. Transdermal HRT bypasses the liver almost entirely, making it the preferred route for women with existing liver conditions. Standard liver markers: ALT, AST, GGT, ALP, bilirubin.

Why the Route of HRT Matters for Your Blood Tests

The delivery method of your HRT affects which blood markers are most important to monitor:

Marker	Oral HRT	Transdermal HRT
Oestradiol blood level	Less reliable (first-pass effect)	Reliable — use for dose adjustment
SHBG	Raised (may worsen symptoms)	Minimal effect
Triglycerides	Can increase significantly	Neutral or improved
TBG (thyroid binding)	Raised (may affect thyroxine dose)	Minimal effect
Liver function	Monitor regularly	Less of a concern
Clotting risk	Slightly increased	Not increased

This is one of the reasons many menopause specialists now default to transdermal oestrogen — fewer metabolic disruptions, more reliable blood level monitoring, and no increase in clotting risk.

When to Test on HRT

• Baseline: Before starting HRT — hormones, thyroid, lipids, liver function
• 6-8 weeks after starting or changing dose: Oestradiol, FSH, thyroid (if on thyroxine)
• 3-6 months: Full panel including lipids and liver function
• Annually: Comprehensive repeat to ensure levels remain therapeutic and no metabolic shifts have occurred
• At trough: Always test just before your next dose, patch change, or gel application

Which Lola Health Test Should You Choose?

The Female Hormones Clarity 31 test (£115) is the best option for HRT monitoring. It covers oestradiol, FSH, LH, progesterone, testosterone, SHBG, a full thyroid panel (TSH, FT3, FT4), and cardiovascular markers — giving you a complete picture of how your HRT is working and whether any adjustments are needed.

For a focused check on reproductive hormones without the wider metabolic panel, the Female Hormones 7 test (£95) covers the core hormone markers and is suitable for quick follow-up tests between comprehensive panels.

Your HRT Should Be Working for You

HRT is not one-size-fits-all. The dose that resolves hot flushes for one woman may leave another still symptomatic. The route that works perfectly for your friend might cause side effects for you. Blood tests are how you move from guesswork to precision — confirming that your oestradiol is in the therapeutic range, your thyroid isn't being disrupted, and your metabolic markers are heading in the right direction.

Take charge of your HRT monitoring. Order the Female Hormones Clarity 31 test and know exactly where your hormones stand — not just that you're "on HRT," but that your HRT is actually working.