The medication aspect of IVF is one of the aspects most patients feel least prepared for when they start treatment. The list of drug names, the injection training session, and the fridge full of medication can feel overwhelming — even to patients who have researched the process thoroughly.

This guide explains the purpose of each medication type, when it is given, and what to expect from it.

Overview: Why Medication Is Needed

A natural menstrual cycle produces one dominant follicle and one egg. IVF requires multiple eggs to improve the chances of creating viable embryos, so the ovaries are stimulated to develop multiple follicles simultaneously using hormone medications.

Alongside this, medications are used to prevent premature ovulation, to trigger final egg maturation, and to support the uterine lining after egg collection.

Phase 1: Suppression (Long Protocol Only)

In a long protocol (less common now, but still used), treatment starts with a period of ovarian suppression before stimulation begins. This is done using:

GnRH agonists (brand names: Buserelin, Nafarelin as a nasal spray; Lupron by injection)

These drugs initially cause a brief surge of FSH and LH, then suppress their production, putting the pituitary gland into a "quiet" state. The goal is to prevent natural hormone fluctuations from interfering with the controlled stimulation that follows.

Side effects mirror those of menopause — hot flushes, mood changes, headaches, disrupted sleep. These are temporary and resolve when the drug is stopped.

The antagonist protocol (now the more common approach) skips this phase entirely and uses a different suppression drug later in the cycle.

Phase 2: Stimulation

FSH (follicle-stimulating hormone) — the core stimulation drug

FSH drives follicle growth. In a natural cycle, FSH rises briefly to stimulate one follicle to dominance; in IVF, higher doses over a longer period stimulate multiple follicles.

Common brand names: Gonal-F, Bemfola, Menopur (which contains both FSH and LH), Fostimon, Rekovelle (recombinant FSH). Most are supplied in pre-filled pens with fine needles for subcutaneous (under-skin) injection, usually into the abdomen.

Typical dose: 75–450 IU daily, depending on ovarian reserve (see AMH and NHS IVF eligibility).

Duration: 10–14 days, with monitoring scans at days 5–7 and again when follicles approach target size.

Side effects: Abdominal bloating and discomfort (particularly as follicles enlarge), breast tenderness, mood sensitivity. These are expected and not signs of a problem unless severe or rapid in onset (which could signal early OHSS).

Phase 3: Preventing Premature Ovulation (Antagonist Protocol)

In an antagonist protocol, a GnRH antagonist is introduced once the leading follicles reach approximately 12–14mm, typically around Day 5–7 of stimulation.

GnRH antagonists (brand names: Cetrotide, Orgalutran)

These drugs block LH receptors and rapidly suppress LH, preventing premature ovulation of the developing follicles. The suppression takes effect within hours rather than the weeks required by agonist down-regulation.

The injections are given daily from the day the antagonist is started until the trigger injection.

Side effects are generally mild — local injection site reactions, occasional headache. The drug does not cause the menopausal-type symptoms of GnRH agonists.

Phase 4: Trigger Injection

When the leading follicles reach their target size (typically 17–20mm), a trigger injection is given to cause final egg maturation and prepare the eggs for collection 34–36 hours later.

hCG trigger (brand names: Ovitrelle, Pregnyl)

hCG (human chorionic gonadotrophin) mimics the natural LH surge that triggers ovulation in a normal cycle. The timing is precise — the trigger injection is timed exactly 34–36 hours before the scheduled egg collection. Missing or getting the timing wrong can result in an empty collection.

hCG triggers carry a higher OHSS risk in susceptible patients (particularly those with PCOS or a high follicle count) because hCG has a longer half-life than LH.

GnRH agonist trigger

An alternative to hCG, used in patients at high OHSS risk. A single dose of GnRH agonist (e.g., Buserelin, Leuprorelin) causes the pituitary to release a brief natural LH surge, which is shorter-lived than hCG and substantially reduces OHSS risk. It can only be used in an antagonist protocol (not a long protocol, since the pituitary is already suppressed).

Phase 5: Luteal Support

After egg collection, and through the embryo transfer and two-week wait, the uterine lining must be supported. In a stimulated IVF cycle, the hormonal state after egg collection does not naturally support the luteal phase in the same way it does in a natural cycle.

Progesterone — the key post-collection drug

Progesterone prepares and maintains the endometrium for implantation. Common forms:

Vaginal pessaries: The most commonly used route in the UK. Brand names include Cyclogest, Utrogestan. These are inserted vaginally (or sometimes rectally) typically 2–3 times daily. The main side effects are discharge and occasional discomfort.

Vaginal gel: Crinone 8% gel is an alternative used by some clinics, applied once daily.

Intramuscular injections: Used less commonly as a first-line route in the UK but sometimes recommended for patients where vaginal absorption is suboptimal. More painful than pessaries.

Oral progesterone (Utrogestan): Some evidence for equivalent effectiveness to vaginal, and easier to take.

Progesterone continues until approximately 10–12 weeks of pregnancy if the cycle is successful. Stopping prematurely risks pregnancy loss. If the cycle does not result in pregnancy, progesterone is stopped after the pregnancy test.

Oestrogen — used in medicated FET cycles

For frozen embryo transfers in an artificial (medicated) cycle, oestrogen (typically oral estradiol valerate, brand name Progynova) is taken for 10–14 days before progesterone is added to prepare the endometrium. See frozen embryo transfer guide for more detail on FET protocols.

Practical Notes on Injections

Most stimulation medications come in pre-filled pens with dial-and-inject systems. The needles are fine-gauge and subcutaneous — most patients find them less intimidating in practice than expected.

Your clinic's nurse will provide injection training before you start. Most patients or partners learn quickly and find the injections manageable within a day or two. Common advice:

  • Rotate injection sites across the abdomen (left side, right side, varying position)
  • Let the pen reach room temperature before injecting if stored in the fridge
  • Ice the area first if you are particularly needle-averse
  • Keep a medication schedule chart to track timing

Frequently Asked Questions

Q: What happens if I miss an injection?

A: Contact your clinic immediately. For stimulation injections, missing a day is not necessarily catastrophic but the clinic needs to know to advise on whether to adjust the schedule. For the trigger injection, timing is critical — if you realise you have missed or are significantly late on the trigger, call your clinic's out-of-hours line immediately.

Q: Can I travel during my IVF cycle?

A: Stimulation medications need refrigeration and must be brought in hand luggage with a letter from your clinic. Travel during monitoring is generally manageable if the destination has a facility to do scans, but most patients prefer to stay close to home during the stimulation phase for monitoring flexibility.

Q: Why do I need to continue progesterone if the test is positive?

A: In a natural pregnancy, the corpus luteum (the remnant of the follicle after ovulation) produces progesterone until the placenta takes over at approximately 8–10 weeks. In IVF, the corpus luteum function is disrupted by the egg collection process, so exogenous progesterone is needed to substitute until the placenta is established.

Q: Are IVF medications safe?

A: The medications used in IVF have been in widespread use for decades. The primary risks are OHSS (see IVF timeline) and, at a population level, there has been extensive study of cancer risk — particularly ovarian cancer — in IVF patients, with current evidence showing no meaningful increase in risk attributable to IVF medication specifically.

This article is for information only and does not constitute medical advice. Medication protocols vary between clinics; follow your clinic's specific instructions.