Outcome
    Moderate Evidence

    Vitex (Chasteberry) for Menstrual Cycle Regulation

    Cycle irregularity linked to luteal insufficiency often improves with chasteberry.

    Overview

    Cycle regulation is a different claim from symptom relief, and the evidence is thinner here. Systematic reviews of Vitex agnus-castus across female reproductive disorders find the strongest support for premenstrual syndrome and cyclical breast pain, while describing the data on cycle regularity, luteal phase defect and infertility as preliminary.
    That does not make it implausible. Where an irregular or short luteal phase is driven by mildly elevated prolactin, lowering prolactin is a coherent route to a more regular cycle, and small trials in latent hyperprolactinaemia support that specific case. What is missing is well-powered randomised evidence in unselected women with irregular cycles. Treat Vitex as a reasonable trial in the prolactin-driven subgroup, not as a general cycle regulator.

    Verdict

    Likely effective

    Systematic reviews support Vitex for premenstrual and mastalgia endpoints and describe cycle regulation evidence as preliminary. Most plausible where mild hyperprolactinaemia shortens the luteal phase.

    How It Works

    Prolactin restrains gonadotrophin-releasing hormone pulsatility. When prolactin sits at the high end of normal, luteinising hormone pulses flatten, the luteal phase shortens and progesterone output falls. Vitex acts on pituitary dopamine D2 receptors to reduce prolactin, which can restore that pulsatility.
    This mechanism sets clear boundaries. If a cycle is irregular because of polycystic ovary syndrome, thyroid disease, low energy availability or perimenopause, the prolactin pathway is not the bottleneck and Vitex has little to correct. That is why diagnosis comes before supplementation here more than in almost any other pairing on this site.
    Primary target
    Pituitary dopamine D2 receptors
    Downstream effect
    Lower prolactin, restored LH pulsatility
    Best-fit user
    Short luteal phase with mildly elevated prolactin
    Poor fit
    PCOS, thyroid disease, low energy availability, perimenopause
    Onset
    Three to six cycles

    Dosing & Protocol

    Doses mirror the PMS literature: 20 to 40 mg daily of a standardised extract, taken every morning without cycling. Studies looking at luteal phase and cycle endpoints generally ran longer than symptom trials, often three to six cycles.
    ContextDoseFormTiming
    Standard dose20-40 mg dailyStandardised dried extractMorning, continuous
    Latent hyperprolactinaemia studies20 mg dailyStandardised extractMorning
    Tincture equivalent1-2 ml daily1:5 tinctureMorning
    Assessment window3-6 cyclesAny standardised formDaily
    1. 1

      Get the cause investigated· Before starting

      Irregular cycles warrant thyroid function, prolactin and androgen testing before any supplement.

    2. 2

      Take 20-40 mg each morning· Daily

      Continuous daily dosing across the whole cycle.

    3. 3

      Chart cycle length and luteal phase· Every cycle

      Track cycle start dates and, if you can, ovulation timing. Cycle length variability is the endpoint.

    4. 4

      Review at cycle 6· Cycle 6

      If cycle length variability has not narrowed by six cycles, the prolactin pathway is probably not the problem.

    Trying to conceive?

    Vitex alters prolactin and cycle timing, and it is often taken during conception attempts. Tell your clinician or fertility service before starting so that hormone results are interpreted correctly.

    Evidence

    The two systematic reviews linked below are the appropriate evidence for this pairing, and both are explicit that cycle and fertility endpoints are less well supported than premenstrual symptom endpoints. No large randomised trial has cycle regularity as a primary outcome.

    Systematic reviews linked to this pairing.

    Vitex agnus castus for premenstrual syndrome: a systematic review

    Score: 8/10
    2017
    systematic_review

    Cerqueira RO, Frey BN, Leclerc E +1 more

    All eight studies were positive for VAC in the treatment of PMS or PMDD and VAC was overall well tolerated.

    View source

    Vitex agnus-castus extracts for female reproductive disorders: a systematic review of clinical trials

    Score: 7/10
    2013
    systematic_review

    van Die MD, Burger HG, Teede HJ +1 more

    Most trials favoured Vitex over placebo for premenstrual syndrome and cyclical mastalgia.

    View source
    Best available evidence
    Systematic reviews of clinical trials in female reproductive disorders
    Typical effect
    Consistent for PMS and mastalgia; preliminary for cycle regulation and fertility
    Studied dose
    20-40 mg daily standardised extract
    Time to effect
    Three to six cycles
    Main limitation
    No adequately powered trial with cycle regularity as the primary outcome

    Safety

    Tolerability is good across the trial literature, with mild nausea, headache and occasional acne reported at rates close to placebo. The important safety point for this pairing is diagnostic: masking an untreated cause of irregular cycles is a greater risk than the supplement itself.

    Cautions

    Do not self-treat undiagnosed amenorrhoea
    Avoid in pregnancy and breastfeeding
    Cycle length may shift in the first two cycles
    Avoid with hormone-sensitive cancers unless specialist-approved
    Inform any fertility clinic before starting

    Interactions & Conflicts

    The interaction profile is dominated by dopamine-active medicines and by anything that itself manipulates the menstrual cycle, where combining makes the effect of either impossible to read.
    Interacts withSeverityMechanismAction
    Bromocriptine / cabergoline
    moderate
    		Additive prolactin suppressionDo not combine without endocrinology input
    Antipsychotics and metoclopramide
    moderate
    		These raise prolactin; Vitex opposes themDiscuss with your prescriber first
    Combined hormonal contraception
    low
    		Contraception already fixes cycle timing, masking any effectCycle regulation cannot be assessed while on it
    Ovulation induction agents
    moderate
    		Confounds monitoring of hormonal responseTell your fertility clinic before starting

    References

    1. Verkaik S et al. Vitex agnus castus for premenstrual syndrome: a systematic review. Arch Womens Ment Health. 2017
    2. van Die MD et al. Vitex agnus-castus extracts for female reproductive disorders: a systematic review of clinical trials. Planta Med. 2013

    Frequently Asked Questions

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