Does the timing of this injection really matter that much?

Yes, the trigger is timed precisely by your clinic and egg retrieval is scheduled around it, so always confirm exact timing with your clinic rather than estimating.

Will Ovitrelle show up on a pregnancy test?

Because it contains hCG, it can cause a false positive on a home pregnancy test for a period afterwards. Ask your clinic when it is appropriate to test.

What if I am not sure the injection went in properly?

Contact your clinic immediately, since the timing of egg retrieval depends on this injection.

Does it need to be refrigerated?

Check the patient information leaflet, as storage can depend on whether the pen has been used before.

Trigger injection (human chorionic gonadotrophin)

Ovitrelle

Also known as Choriogonadotropin alfa, hCG trigger injection

Written by Zayn Miah & R KhanomLast updated 17 September 2026Not clinically reviewed

Ovitrelle contains a lab-made form of human chorionic gonadotrophin (hCG), given as a single injection under the skin using a pre-filled pen.

Why it may be used

It is used to complete the final maturing of the eggs inside the follicles and to time ovulation, so that egg retrieval can be scheduled at the right point after the injection.

Where it fits in a cycle

It is given once, near the end of the stimulation phase, at a time worked out precisely by your clinic based on scan and blood test results. Its timing relative to egg retrieval is set by the clinic and should not be adjusted.

Side effects listed in the patient leaflet

Injection site pain, redness or bruising
Headache
Abdominal pain or bloating
Nausea
Fatigue
Mood changes
Ovarian enlargement or discomfort after the trigger

When to ring the clinic

•Rapid or severe abdominal swelling in the days after the injection
•Severe abdominal or pelvic pain
•Breathlessness
•Markedly reduced urine output
•Sudden weight gain, which can be a sign of ovarian hyperstimulation syndrome (OHSS)

Questions people ask

Does the timing of this injection really matter that much?: Yes, the trigger is timed precisely by your clinic and egg retrieval is scheduled around it, so always confirm exact timing with your clinic rather than estimating.
Will Ovitrelle show up on a pregnancy test?: Because it contains hCG, it can cause a false positive on a home pregnancy test for a period afterwards. Ask your clinic when it is appropriate to test.
What if I am not sure the injection went in properly?: Contact your clinic immediately, since the timing of egg retrieval depends on this injection.
Does it need to be refrigerated?: Check the patient information leaflet, as storage can depend on whether the pen has been used before.

Safety

This page provides general information only and does not replace advice from your fertility clinic.
The exact timing of this injection must come from your clinic's written instructions, since it is closely tied to your retrieval date.
The patient information leaflet in the box is the authoritative reference for this medicine.
Tell your clinic about other medicines, allergies and medical conditions before use.

Sources

Patient information leaflets and product characteristics, electronic medicines compendium (emc). Link checked 17 September 2026.
IVF: what is IVF and how does it work?, HFEA (UK fertility regulator). Link checked 17 September 2026.

Written by patients, not clinicians. This page has not yet been reviewed by a named fertility professional, so it explains published guidance and points you to the original source instead of giving medical advice. It is not medical advice. Decisions about your treatment belong with your own clinic. Read our editorial policy and corrections policy.