Hormone testing? The right moment is everything

With hormone testing, timing is key: a few hours or days difference can greatly affect your results. Measuring hormones like FSH, LH, estradiol and progesterone at the right time in your cycle gives you a reliable picture of your hormonal balance, fertility or menopause. With the right timing and hormone tests via Bloedwaardentest.nl you can avoid misinterpretation and measure what is really relevant.

Hormones fluctuate from hour to hour and day to day. A few days or even a few hours difference can affect your results. Therefore, timing is crucial in hormone testing, whether you want to understand your cycle, have a desire to have children, are going through menopause or are taking hormone supplementation.

Key advice:
Always follow the lancing time indicated by your doctor, midwife or fertility clinic.

But to prepare you properly, below is an overview of the most commonly used hormones, when they should ideally be measured and why.

Why timing is so important

Hormones work in rhythms:

• Monthly rhythm → estrogen, progesterone, FSH, LH
• Daily rhythm → prolactin, cortisol
• Pulse release → progesterone and LH
• Cycle independent → AMH

So the time of pricking determines whether you get a reliable picture or a biased result.

Most advised sampling times per hormone

FSH, LH & Estradiol

• Best time: Day 2-5 of the cycle
• Why: This gives the most stable and reliable picture of your basic hormonal status and indirectly your ovarian reserve.

Progesterone

• Best time: about 7 days before your next period
  (More commonly known as "day 21 test" on a 28-day cycle)
• Why: Progesterone peaks in the luteal phase, only when you've had ovulation. This is how you assess:
• Whether you have ovulated
• How strong your progesterone production is
• Whether your luteal phase is sufficient

With longer or shorter cycles, this time shifts with you.
In fertility testing, progesterone is sometimes measured 2× (day 21 + day 24-26) to catch the peak.

AMH

• Best time: Any day of the cycle
• Why: AMH is cycle-independent and ideal for determining your ovarian reserve.

Prolactin & TSH

• Best time: Morning (preferably sober)
• Why: prolactin has a strong diurnal rhythm; TSH can fluctuate slightly due to diet, stress and time of day.

Hormone testing for an irregular cycle

With PCOS, perimenopause or an irregular cycle, it is sometimes not possible to choose a fixed day.

FSH, LH, estradiol, if possible day 2-5
AMH, always reliable
Progesterone, often not very predictive unless repeated because ovulations can skip

Measure hormones at menopause (perimenopause & postmenopause)

Perimenopause (fluctuating cycle)

• Hormones fluctuate greatly
• Progesterone can be low as ovulations drop off
• Doctor usually chooses a measurement time based on symptoms

Postmenopause (no more cycle)

• Estradiol stable low
• FSH and LH stable high
• Progesterone virtually impossible to measure, usually not useful unless:
• you are taking hormone supplementation
• doctor wants to check something specific

Practical tips: how to make your hormone test reliable

1. Always note the date and time

Indispensable for the doctor and lab, especially with:

• progesterone
• prolactin
• cortisol

2. Need a weekend? Just can.

Your ideal puncture time sometimes falls on the weekend. That's not a problem:
many lancing stations are open on Saturdays
you can submit blood via a medical lab mailbox that is also emptied on weekends
always have the date and time written on the form

3. Finger prick tests available

For progesterone, TSH and other hormones, among others:

• prick yourself at home
• Send via medical PostNL mailbox (it is emptied daily)