What the trigger shot actually does
Throughout the stimulation phase, the daily injections work on growing multiple follicles Fluid-filled sacs in the ovaries, each containing a developing egg. at the same time. The trigger shot is what tells those follicles to release their eggs.
More specifically, it initiates the final maturation stage that eggs go through before they can be frozen. Only mature eggs Eggs that have completed their development and are ready to be fertilized or frozen. Immature eggs retrieved cannot be frozen. can be frozen — immature ones can't. The trigger shot is what gets them there.
Without it, retrieval doesn't happen. It's the last injection of the process, and the one where the timing is almost entirely out of your hands — your nurse gives you the time, and that's the time.
From my orientation notes
My nurse described it as the shot that "finishes the job" everything else has been building toward. After weeks of injections on my schedule, this one was on the eggs' schedule. That framing actually helped me take it seriously.
Why timing is everything
The clinic gives a specific time for the trigger shot — not a window, not a rough estimate. A specific time. That's because retrieval is scheduled exactly 34 to 36 hours later, and it has to happen before natural ovulation does.
Too early and the eggs won't be mature enough to retrieve. Too late and they may have already ovulated — and they'd be gone. The window is real. This is one of those moments where precision actually matters.
Worth knowing — this one is time-critical
The trigger shot gets taken at the exact time the nurse assigns. That time is chosen based on when retrieval is scheduled. A significant miss — an hour or more in either direction — can affect the outcome or cancel the cycle entirely. I set two alarms. It felt excessive until I remembered what was at stake.
Most clinics schedule trigger shots in the evening — often somewhere between 9pm and midnight — because that puts retrieval in the morning roughly 34–36 hours later, when procedures typically run. The specific time depends on each person's follicle development and clinic schedule.
Ovidrel vs. Lupron — the two types
There are two main trigger shot options used in egg freezing. Which one a doctor prescribes depends on hormone levels, response to stimulation, and the risk of OHSS Ovarian Hyperstimulation Syndrome — a complication where the ovaries over-respond to stimulation medications, causing swelling and discomfort. In rare cases it can be severe. . It's typically not known which one will be used until closer to trigger day — which is one reason holding off on buying it makes sense.
| Type | How it works | When it tends to be used |
|---|---|---|
| Ovidrel (hCG) | Contains hCGHuman chorionic gonadotropin — a hormone that mimics the natural LH surge that triggers ovulation., which mimics the natural hormone surge that causes eggs to release | The more common option; typically used when OHSS risk is low to moderate |
| Lupron (Leuprolide) | Triggers the body's own LH surgeA rapid rise in luteinizing hormone that signals the ovaries to release mature eggs. rather than adding hCG directly | Often chosen when OHSS risk is higher — it tends to lower that risk |
| Dual trigger | Both Ovidrel and Lupron together | Sometimes used to optimize egg maturity in certain situations |
One practical difference: the next period arrives at different times depending on which was used. After Ovidrel, it tends to come roughly two weeks post-retrieval. After Lupron, closer to one week. Something worth knowing so it's not a surprise.
The doctor and nurse decide which type based on how the cycle is going. It's not something that needs to be figured out in advance — just worth knowing that the options exist and that they're different.
When to buy it
This is something I really wish someone had told me at the start: the trigger shot is worth waiting to buy until the nurse confirms which type is needed.
As follicles approach the right size during monitoring, the nurse gives a heads-up that trigger day is coming. Once the type is confirmed, ordering it that same day makes sense — it'll often be needed that evening. Some specialty pharmacies turn it around same-day; others need more notice. It's worth calling ahead once things start looking close.
Something I learned
This same idea applies to all the medications — the NYU Langone orientation actually advises picking up only the first half of everything to start, since you may not end up needing all of it. The trigger shot is the clearest example: there's literally no way to know which type is needed until the doctor sees how the body is responding. Buying too early means potentially paying for something that ends up unused.
People buy the trigger shot at orientation — months before they need it — because it feels responsible to be prepared. But you genuinely can’t know which type you need until the nurse confirms it based on your response. Buying it early means potentially paying for the wrong one. Wait. The nurse gives you enough notice to order same-day if needed. This is one case where preparation early is actually the wrong move.
What it's actually like to take
The trigger shot is a subcutaneous injection An injection into the fatty layer just beneath the skin — not into muscle. Typically given in the abdomen. — the same kind as everything else during stimulation. The mechanics aren't different.
Ovidrel comes pre-filled in a pen. Lupron gets drawn from a vial. Both go in the abdomen. Clinics include injection training videos for both — after doing daily stimulation injections, this one isn't technically harder. It's just one shot, once.
Everyone's experience afterward is different. Some people feel nothing unusual. Others notice bloating, mild cramping, or a sense of fullness in the next few hours as follicles prepare to release. That's generally considered normal. What's worth flagging to a doctor: severe pain, significant bloating, or rapid weight gain.
What I'd tell a friend
Wait until the nurse tells you which trigger type you need before buying it. This sounds obvious but people buy it early because they want to be prepared, and then they either buy the wrong one or buy it before knowing if their cycle will even reach trigger day. The nurse confirms the type the day before or the morning of — there's enough time to order or pick it up. Don't buy early.
What surprised me
That the trigger shot timing is the most precise thing in the entire process. Everything else has some flexibility — monitoring appointments can shift by a day, injection times can vary by an hour or two. The trigger shot has to happen within a specific 30-minute window or the entire cycle is affected. That precision was something I hadn't fully internalized until the nurse explained it very directly.
Audio note coming soon — what trigger night actually felt like, in my own words.
What comes next
After the trigger shot, retrieval is set. The clinic will have already confirmed the procedure time when giving the trigger instruction — those two things happen together.
One thing that's standard for any procedure involving anesthesia: nothing to eat or drink for 8 hours beforehand. The nurse gives the specific cutoff time when confirming the retrieval appointment.
The other injections — gonadotropins Hormones used to stimulate the ovaries — FSH (Gonal-F or Follistim) and HMG (Menopur). The main daily injections throughout stimulation. and the GnRH antagonist Medications like Cetrotide or Ganirelix that prevent premature ovulation during stimulation. — stop after the trigger. The nurse confirms when.
The day before retrieval is a good one to use for practical prep: arranging a ride home (driving or walking alone isn't recommended for 6–8 hours post-procedure), setting up somewhere comfortable to rest, and having someone available to check in. The procedure itself is quick. The day after tends to be slower.
From here it goes straight to retrieval. The Egg Retrieval page covers what that day actually looks like.