What if I Make a Mistake With My hCG Trigger Shot?

Fertility treatments are expensive and stressful, and for many of us, we only have a window of a few cycles to get it right. That makes every single step of the process incredibly important, which only adds to the overall anxiety. Sigh.

For those who are new to the world of Assisted Reproductive Technology (ART), some IVF and IUI protocols require you to inject yourself with human chorionic gonadotropin (hCG) at a very specific time during your ovulation cycle. Also known as the "trigger shot," this can be a lot of added pressure for someone without a Doctorate in Pharmacy.

Getting the timing of the trigger shot wrong can potentially set you back an entire month of treatment, which is why it's important to understand what the hCG trigger shot is, why it’s needed, and what to do if you make a mistake with yours. Now let's dive in.

What is the hCG trigger shot?

The hCG trigger shot is an injection of human chorionic gonadotropin, a hormone that tells your ovaries it’s time to finish maturing your eggs. In IVF and IUI cycles, this step is essential because it helps your care team control exactly when ovulation happens. According to 2014 research for Gynecological Endocrinology, hCG acts very similarly to luteinizing hormone, which is the natural hormonal surge that triggers final egg maturation before ovulation. By delivering hCG at a precise time, your clinic can help the eggs complete their final growth stage and prepare for either fertilization in the body during an IUI or retrieval during an IVF cycle. Common brands you might come across include Pregnyl, Ovidrel, and Novarel. Timing is everything with this medication. Your clinic will schedule the shot down to the hour because this sets the clock for what comes next in your treatment plan.

The hCG injection (also known as a "trigger shot") helps mature and release eggs from the ovaries and is an important part of the IVF process. It's completely normal to feel a bit nervous about administering the shot; nobody likes needles, especially under pressure! However, if you understand how it works and set an alarm to ensure that you do it at the right time, you’re very unlikely to make a mistake.

It's crucial to keep in mind that the hCG trigger shot is usually administered about 36 hours before an egg retrieval procedure (this timing may differ slightly with IUI procedures). This allows the egg to mature and release from the ovary, which is necessary for fertilization. If you don't administer the shot at the correct time, it's possible that the egg(s) may not be mature at the time of retrieval.

hCG trigger shot mistakes: What can go wrong?

It’s totally normal to worry about messing up your trigger shot. This is one of the most time sensitive moments in an IVF or IUI cycle, and the stakes can feel sky high. The good news is that most people do not make serious mistakes. Clinics build clear instructions, reminders, and buffer time into your protocol because they know you’re human and things happen. Still, there are a few common worries that come up again and again, and it helps to understand what actually matters, what’s usually fixable, and when you should call your clinic right away. Below, we’ll walk through the most common trigger shot mistakes and what to do next.

Taking the trigger shot too late or too early

Most clinics time the hCG shot about 36 hours before egg retrieval. That window supports final egg maturation and predictable ovulation. If you take the shot significantly too early, your eggs may not complete their final growth phase, which lowers the chance of retrieving mature eggs. If you take it too late, ovulation may start before your retrieval, which can lead to empty follicles. Late ovulation is one of the main risks when the shot is delayed by several hours.

This is where everyone asks about the tiny timing deviations. If you were 5 minutes late, you’re fine. Even a 1 to 2 hour shift is usually manageable as long as you let your clinic know. Once you reach bigger gaps, like 4 to 6 hours, timing becomes more complicated and may require adjusting your retrieval or, in some cases, postponing the cycle.

If you administer your hCG trigger shot at the wrong time, your fertility specialist may recommend postponing the egg retrieval procedure until your next menstrual cycle. It really depends on how many hours you were too early or too late. That's why it's important to keep your fertility specialist in the loop. Life happens: traffic, sick children, unexpected phone calls. But if you were only out by a couple of hours, try not to panic. Your specialist may be able to move your egg retrieval appointment to later in the day to make up for the lost time.

If you’re way off with your shot, however, you’ll probably have to go through the entire process again, including taking medications and undergoing fertility testing. As you can imagine, this is best avoided, so try to plan your day around making sure you have enough time to correctly administer your trigger shot. The right timing and triple-checking your dosage can make a massive difference in the outcome of your cycle.

Wrong dosage of hCG trigger shot

Another potential mistake that patients make with the hCG trigger shot is administering the wrong dose. The dosage of hCG that you'll be given is based on your specific treatment plan and is tailored to your needs. If you accidentally give yourself too much or too little of the medication, it could affect the timing and success of the egg retrieval procedure. Too little may not give your ovaries the hormonal signal they need, and too much can increase your risk of ovarian hyperstimulation in certain patients.

If you're unsure about the correct dosage of the hCG trigger shot, it's important to reconfirm with your fertility specialist, nurse, or pharmacist. They'll be able to give you the correct information and ensure that you're administering the medication safely and effectively.

If you realise you may have taken the wrong dose, call your clinic immediately so they can decide whether to adjust timing, monitor you sooner, or postpone your cycle.

Wrong injection site or technique

Depending on the brand, your trigger shot may be given under the skin or into the muscle. Ovidrel is usually subcutaneous, while some formulations of Pregnyl or Novarel may be intramuscular. If you accidentally inject in the wrong place, the medication may absorb more slowly but often still works. Mild discomfort or a small bruise is common and not typically dangerous. Call your clinic if you’re unsure whether enough medication was delivered or if you think the injection was too shallow or missed the correct site altogether.

Broken syringe or supply issues

Nothing spikes stress quite like a syringe snapping mid prep or discovering you’re missing a needle when the clock is ticking. If a syringe cracks, if medication spills, or if you’re unsure how much made it into the syringe, don’t try to piece together a partial dose. Call your clinic or their after hours line. Many clinics keep backup medication on site or can direct you to a local pharmacy with emergency stock. It’s a good idea to open your supplies earlier in the day to check you have everything you need so these surprises happen before the countdown starts.

Other common trigger shot mistakes

A few other things come up but tend to be minor. Small air bubbles in the syringe usually aren’t harmful. If your medication requires mixing and you forget a step, call your nurse and ask whether you should remake the dose. Some hCG brands require refrigeration, and leaving them out briefly is unlikely to ruin them, but long periods at room temperature can affect potency. Again, when in doubt, call. Your clinic would much rather talk you through a quick check than have you sit at home spiralling.

IVF trigger shot timing: Why it matters so much

The timing of your IVF trigger shot is one of the most carefully planned parts of the entire cycle. Clinics schedule it with such precision because the hCG signal kicks off the final stage of egg development. According to a 2016 review for the International Journal of Reproductive BioMedicine, hCG acts like a controlled version of your natural luteinizing hormone (LH) surge, which normally triggers ovulation about 36 hours later. That 36 hour window gives your eggs enough time to complete their final maturation steps but not enough time to release on their own before retrieval.

Your retrieval appointment is built around this exact biology. When the trigger is given too early, the eggs may not reach optimal maturity. When it’s too late, ovulation can start before the retrieval team gets to the follicles. Both situations reduce the number of mature eggs available. Even small timing mistakes can shift the way your ovaries respond, which is why your monitoring appointments matter so much. Those ultrasound and bloodwork checks help your team calculate the best moment to trigger based on follicle size and hormone levels, not just the calendar.

Can you ovulate before trigger shot?

This is a very real fear for a lot of patients, but premature ovulation before the trigger shot is uncommon. Care teams watch your estradiol levels and follicle measurements closely. Rising LH levels or sudden pelvic discomfort can be early signs of spontaneous ovulation, and most clinics monitor these patterns specifically to avoid it. If premature ovulation does happen, retrieval may be cancelled because the eggs are no longer in the follicles. It’s frustrating, but it’s also rare when you’re being monitored regularly.

Can you ovulate 12 hours after trigger shot?

Ovulating 12 hours after the trigger shot would be extremely early. Most people ovulate between 36 and 40 hours after hCG is given, which matches data reported in reproductive endocrinology textbooks and NICE materials on ovulation induction. That timing consistency is why retrievals are almost always scheduled the morning after the 36 hour mark. There’s always some individual variation in hormone response, but 12 hours would fall far outside the expected biological pattern.

How do you know if hCG trigger shot worked?

Here’s the truth most people aren’t told before their first trigger: you usually can’t feel it working. The hCG trigger shot sets off a hormonal chain reaction that helps the eggs finish maturing, but those changes happen at the cellular level. As explained in a 2017 study for the Journal of Assisted Reproduction and Genetics, hCG mimics your body’s natural luteinizing hormone surge, which triggers final egg maturation in the 36 hours before ovulation. That’s a lot of biology happening behind the scenes, not something that reliably creates physical symptoms.

Some people notice mild bloating, light cramping, or breast tenderness after the trigger, but many feel absolutely nothing. Both scenarios are normal. A lack of symptoms does not mean the shot didn’t work, and feeling “nothing” is incredibly common.

The real confirmation comes from your monitoring and your retrieval. Your clinic times the trigger based on follicle size and hormone levels, which gives them a clear picture of how prepared those follicles are. You don’t need to symptom spot because the science is already doing the heavy lifting. At retrieval, your doctor can see whether the follicles responded as expected, how many eggs were released, and how many were mature. That’s the first definitive sign the trigger did its job.

So if you’re sitting at home wondering whether you should feel different, you’re not alone. Most people won’t have any obvious signs. Trust the timing, trust the monitoring, and let your care team confirm the results at retrieval.

What happens if you miss an IVF injection?

Missing an IVF injection can feel terrifying in the moment, but what it means for your cycle depends on which medication you missed and how much time has passed. Not all injections carry the same level of urgency. The trigger shot is the most time sensitive medication in an IVF protocol. Stimulation meds like FSH or LH are important too, but missing one dose doesn’t usually carry the same immediate consequences.

If you miss a stimulation injection, your ovaries may receive less hormonal support for that day, which can slow follicle growth. Most clinics will tell you to take the missed dose as soon as you remember, unless it’s very close to your next scheduled injection. Follicle development is monitored through bloodwork and ultrasound, which means your team can often adjust your dose at the next check to keep your cycle on track. A single missed stim shot rarely ruins a cycle, but you should always call your clinic right away to confirm what to do.

If you miss the trigger shot, the situation is more serious. The trigger sets the precise timing for egg maturation and retrieval. Missing it or taking it at the wrong time can mean the eggs don’t mature properly or ovulation happens before the retrieval team can collect them. In many cases, if the trigger is significantly late, the cycle may need to be postponed. This is why clinics emphasise alarms, reminders, and clear instructions.

When it comes to timing, there’s a general rule: the sooner you loop in your care team, the more options they have. If you realise the mistake within a short window, they may guide you to take the dose immediately or adjust your monitoring. If many hours have passed, there may be no safe way to “make it up,” and postponing the cycle protects your health and your results.

No matter which medication you’ve missed, don’t sit at home spiralling. Your clinic handles situations like this all the time, and they’ll tell you exactly what to do next.

Types of trigger shots: What's the difference?

Trigger shots all aim to do the same thing: send a surge of hCG that tells your ovaries it’s time for the eggs to complete their final stage of maturation. But the formulations aren’t identical, and understanding the differences can help you feel more confident when you’re staring down that little vial or pre filled syringe.

Pregnyl trigger shot

Pregnyl is a urinary derived form of hCG, which means the hormone is purified from human urine and processed for medical use. It’s been around for decades and is widely used in both IVF and IUI cycles. Clinics often prescribe doses like 5,000 IU or 10,000 IU depending on your follicle development and ovarian response. Because Pregnyl is usually supplied as a powder with a separate vial of liquid, it typically requires mixing just before injection. Some formulations need refrigeration while others can stay at room temperature until reconstituted, so it’s important to check the instructions on your specific box.

Ovidrel trigger shot

Ovidrel is a synthetic version of hCG called choriogonadotropin alfa. Because it’s made through recombinant DNA technology rather than being urine derived, it’s very consistent in dosing and purity. One of the main perks is convenience. Ovidrel usually comes as a pre filled syringe, so there’s no mixing, no powder, and far fewer steps. That simplicity is why many clinics choose it when they want to reduce preparation errors.

Compared to Pregnyl, Ovidrel tends to have more predictable absorption, which some clinicians prefer during tightly timed IVF cycles. The most common mistake people worry about with Ovidrel is whether they’ve injected the full dose, especially because the plunger can feel stiff. If you’ve pressed it all the way down and the syringe looks empty, you’ve almost certainly done it correctly.

Novarel trigger shot

Novarel is another urinary derived hCG option, very similar in origin and function to Pregnyl. Like Pregnyl, it usually comes as a powder that must be mixed with sterile liquid before injection, and clinics often prescribe it in doses of 5,000 or 10,000 IU. Some providers choose Novarel when they prefer a specific formulation of hCG or when insurance coverage favors one brand over another. Functionally, Novarel works the same way: it sends the hormonal signal your ovaries need to get those eggs ready for retrieval.

Across all these medications, the biological goal is identical. The differences mostly come down to formulation, ease of use, and clinic preference. Your team chooses the best option for your protocol based on how your follicles are growing and what they believe will give you the most reliable timing.

What to do if you make a trigger shot mistake

If something goes wrong with your trigger shot, the very first thing to do is call your clinic. Not text a friend, not Google every worst case scenario. Call your clinic. They manage medication mishaps every day, and the sooner they know what happened, the more options they have to help you. Timing and dosing decisions during ovulation triggering are highly individualized, which is why your own care team is the only one who can safely tell you what to do next.

When you call, have a few details ready. Note the exact time you intended to take the shot, the time you actually took it, the dose you used, and any concerns like spilling medication, a bent needle, or injecting in the wrong spot. These details help your team decide whether the cycle can continue with adjustments or whether postponing is the safer path. Some mistakes are surprisingly fixable, especially when caught quickly. Others may require rescheduling retrieval to protect egg quality and safety.

Keep your medication records handy, even if that means jotting times on your phone or sticking a Post-it to the counter. This helps eliminate confusion and gives your clinic a clean timeline to work from. Most fertility clinics also have after hours emergency lines, so even if your mistake happens at 11 p.m., you’re not expected to sit with unanswered questions until morning.

And yes, staying calm is easier said than done, but it genuinely makes everything simpler.

We know it’s easier said than done, but if you make an error with your trigger shot, try to stay calm. Medication mistakes happen. You may run out of needles, the syringe may crack, or you could get that essential timing wrong. If you panic, you’re likely to only make things worse. The most important first step is to call your fertility clinic and explain the situation. They'll be able to advise you on the next steps and determine if any changes need to be made to your treatment plan.

It's also a good idea to keep a record of all your medication doses and the timing of when you take them. This can help you keep track of when you took the hCG trigger shot and ensure that you're administering it at the appropriate time.

No matter what happened, you’re not the first person to make this mistake, and your clinic will guide you through the next steps.

Tips to avoid trigger shot mistakes

Here are a few simple habits that make the trigger shot feel less like a high pressure countdown and more like a well rehearsed plan.

• Set multiple alarms: Use your phone, smartwatch, oven timer, whatever you’ve got. Clinics schedule the trigger with precision, so having more than one reminder gives you a buffer if you’re distracted or asleep. It’s a small step, but it can make a big difference when timing matters.
• Have a partner or friend as a backup reminder: Ask someone you trust to text or call you around trigger time. IVF can feel isolating, and sharing the mental load helps you avoid last minute panic. Many patients find that a simple “Are you ready for the shot?” message keeps everything on track.
• Prepare your supplies in advance: Open the box earlier in the day to check that you have needles, syringes, alcohol wipes, and the medication itself. This prevents the very common “I’m missing a needle” chaos that tends to happen at the worst possible moment.
• Double check your dosage with your nurse beforehand: Before the trigger day arrives, confirm the exact dose, whether you’re using a pre filled syringe or mixing vials, and whether the shot is subcutaneous or intramuscular.
• Keep your clinic’s contact info easily accessible: Save the main line and after hours number in your phone. Tape it to the fridge. Put it in your partner’s phone too. If something feels off during preparation, you want to reach someone quickly.
• Do a practice run if you’re nervous: You can rehearse opening the packaging, setting up the supplies, and walking through the steps without actually injecting anything. This helps reduce the “first time jitters” and makes the real moment feel less overwhelming.
• Clear your schedule around trigger time: Avoid meetings, errands, or anything that might delay you. Give yourself a window of quiet, unrushed time so you can focus on getting the steps right without feeling pulled in several directions.

These small precautions help you feel more in control, which is half the battle when everything feels timed to the minute. You deserve as smooth a trigger night as possible.

Moving forward after an hCG trigger shot slip-up

An hCG trigger mistake can hit harder than you expect. You’ve invested time, money, and so much emotional energy into this cycle, so of course it’s upsetting when something doesn’t go to plan. If your cycle needs to be adjusted or postponed, you’re allowed to feel disappointed. Grieve the setback if you need to. It doesn’t mean you’ve failed, and it doesn’t say anything about your strength or your chances moving forward.

Mistakes happen in fertility treatment more often than people admit, which is why your clinic is prepared for these moments. Timely communication with your care team is one of the most important factors in keeping cycles on track. Your team’s job is to guide you, problem solve, and help you understand the safest next step. You’re not expected to carry the burden alone.

Once the initial stress eases, you can look back at what happened and build a plan for next time, whether that means setting more alarms, involving a partner, or prepping supplies earlier. These small adjustments can give you a greater sense of control in a process that often feels anything but.

Making a mistake with your hCG trigger shot can be frustrating and stressful, but it's important to remember that your fertility team is there to support you and help you through the process. If you do make a mistake, don't hesitate to reach out to them for guidance. With the right support, you can get back on track and continue with your fertility treatment, maybe even in the same cycle.

And if this cycle does need to pause, try to zoom out. Your fertility journey isn’t defined by one night, one injection, or one misstep. You’re moving toward your family, even with a few detours along the way.