IVF injections: timing, missed doses, trigger

In the evenings, whilst undergoing stimulation, my phone often rings for the same reason: ‘I gave my injection two hours late’, ‘The pen leaked’, ‘I’m not sure if I injected yesterday’. Almost always, it’s not a problem. But not always, and it depends on the medication in question. Here’s what you need to know before the first evening.

Why a fixed time

Gonadotropins, the medicines that stimulate the ovaries, are taken once a day. Taking them at the same time each day maintains steady blood levels and, above all, makes organisation easier: most clinics schedule injections for the evening, which leaves time to adjust the dose on the same day following the morning ultrasound scan and blood test. The principle and the various regimens are described in the article on stimulation protocols.

A one-hour delay with a gonadotrophin injection generally has no consequences. What does pose a problem is completely forgetting the injection, accidentally taking a double dose, or being late with either of the two injections described below. Choose a time that fits in with your everyday life, including when you’re travelling, and set two alarms.

The antagonist: the injection you must not miss

In the most common protocol today, a second injection is added after a few days of stimulation: the GnRH antagonist, in the form of cetrorelix or ganirelix. Its role is to prevent the hormonal surge that would trigger ovulation too early. If a dose is missed when the follicles are large, ovulation may occur before the egg retrieval, and the eggs will be lost.

This is therefore one of the situations in which you must call the clinic immediately, even late in the evening, without waiting for the next day’s appointment – just as you would if there were an error with the trigger injection or if the warning signs described below were present. The doctor will decide whether to administer an injection straight away, bring forward an ultrasound scan or adjust the schedule.

In the event of a missed or delayed dose

• Never double the next dose to ‘make up for it’. Too high a dose of gonadotrophins increases the risk of hyperstimulation without improving the outcome.
• Make a note of what happened: the scheduled time, the actual time, the dose and the product. This will be the first question you are asked.
• Call or write to the clinic that very evening. The usual advice is to inject as soon as possible if the delay is a few hours, then resume the normal schedule, but you must check with the clinic to confirm this for your specific protocol.
• If the pen has leaked or if you are unsure of the dose, do not re-inject without advice: a partial dose is better than a double dose.

Trigger injection: the time, down to the minute

Once the follicles have reached the correct size, the clinic will give you the exact time for the trigger injection: hCG, or a GnRH agonist in some protocols. This injection initiates the final maturation of the eggs, and the egg retrieval is scheduled accordingly, generally between 34 and 38 hours later, depending on each clinic’s practice. If it is too early, the eggs will not be mature; if it is too late, ovulation may already have taken place. A meta-analysis published in 2023 suggests, in fact, that a delay of slightly more than 36 hours is not detrimental – quite the contrary; however, it is up to the clinic to set the time, and up to you to stick to it.

In practical terms: if the egg retrieval is scheduled for 9.00 am the day after tomorrow, the injection is usually given on the first evening, between 7.00 pm and 11.00 pm, depending on the timeframe chosen by the clinic. Administer it at the specified time, set two alarms, and if you realise there has been a mistake with the time or the medication, call immediately. An error reported straight away can often be rectified by rescheduling the egg retrieval; an error discovered on the morning itself, rarely. The schedule for this day is detailed in the article on egg retrieval.

Time difference and the change of time

Greece is in the Eastern European time zone: one hour ahead of Paris, Brussels or Rome, and two hours ahead of London or Lisbon. The times provided by a Greek clinic, and in particular the time of the trigger injection, are in Greek time. If you are still at home that evening, write down the converted time and have it checked.

For daily injections, the simplest solution is to stick to your usual time and adjust it gradually if necessary, following the clinic’s advice. Also bear in mind the change to summer time and winter time, on the last Sunday in March and the last Sunday in October in the European Union: this is a common source of confusion for a trigger scheduled for that weekend.

On days when you’re flying, plan to take your injection before you leave or upon arrival at your hotel, keeping the pens in your hand luggage. The transport rules are set out in the article on flying.

Steps to avoid most mistakes

• Check the dose displayed on the pen before each injection, and change the needle every time.
• Alternate injection sites on your stomach, a few centimetres from your navel. A slight redness or bruise is common and nothing to worry about.
• Follow the storage instructions in the leaflet: some products need to be kept in the fridge, whilst others can be stored at room temperature for a limited period. Information on conditions in Greece and the cost of products can be found in the article on medicines.
• Keep a notebook or a note on your phone: date, time, product, dose. This will put your mind at rest on evenings when you’re unsure.

Call immediately in the event of significant abdominal swelling, rapid weight gain, shortness of breath, or a widespread skin reaction following an injection.

During their stays in Thessaloniki, my patients have a single number to call, including on the evening of the trigger injection. If you’d like to know how this is organised, please write to me.

Frequently asked questions

Source: https://fertilitegrece.com/en/blog/ivf-injections-timing-missed-dose/ — Triada Baloukoudis, IVF patient coordination in Greece. General information, not medical or legal advice. Printed on

Triada Baloukoudis
Independent IVF patient coordinator in Thessaloniki, with 24 years of experience supporting patients travelling from abroad. More · Contact · Facebook