Fertility · Injection guide
Pregnyl (hCG)® (chorionic gonadotropin)
The trigger shot, mixed from powder. Pregnyl® stands in for your natural LH surge — blood levels peak about six hours in, which is why your clinic gives you an exact hour. It goes into muscle, not under the skin, and the mixing is the fiddly part.
Quick facts
Always follow your clinic's instructions for dose and timing.
What it is
What is Pregnyl (hCG)®?
Human chorionic gonadotropin, or hCG, is a reproductive hormone. Your body produces it in pregnancy — the placenta makes it, and it is what a home pregnancy test looks for. It is built from two subunits, alpha and beta; the alpha subunit is identical to the one in LH, FSH and TSH, and the beta subunit is what makes hCG behave differently from those hormones.
That difference is why it works as a trigger shot. Pregnyl® acts like your body’s own luteinising hormone, stimulating the corpus luteum in the ovary to produce progesterone. In men it stimulates the testes to produce androgens.
Timing is the whole point of this injection. Blood levels rise within about two hours of an intramuscular dose and peak by around six hours — which is exactly why your clinic gives you a specific hour rather than a day.
It arrives as a kit: one 10,000-unit multi-dose vial of white powder and a separate 10 mL vial of sterile solvent. You need both, and you mix them right before you inject.
Normally
- Follicles mature
- Natural LH surge
- Ovulation
On Pregnyl (hCG)®
- Follicles grown by stimulation
- Pregnyl® acts as the LH surge
- Corpus luteum makes progesterone
- Ovulation, on your clinic’s clock
Before you begin
Everything you need, on a clean surface
Storage: unmixed vials at room temperature, 15°C to 30°C. Once reconstituted, the solution keeps for 28 days refrigerated at 2°C to 8°C — never frozen. Discard any leftover once you no longer need it, and never share the vial with another person.
How to inject Pregnyl (hCG)®, step by step
Eight steps. Most of them are the mixing, which is the part patients tell us is hardest to find clear instructions for anywhere else.
Pregnyl® is given into a muscle, not under the skin. Health Canada authorises intramuscular as its only route. If you have been dispensed a different chorionic gonadotropin product, follow that product's own leaflet — and if anything here differs from what your clinic told you, follow your clinic and call us on (905) 235 8820.
- 1
Prep
Getting ready
Wash your hands thoroughly with soap and water. Lay out both vials, your syringe, both needles, alcohol pads and your sharps container on a clean surface. Remove the flip caps from both vials, wipe each rubber stopper with an alcohol pad, and let them dry for at least a full minute.
Pharmacist tip: The multi-dose vial is for one patient only. It is never shared between people, even within a household.
- 2
Mix
Check how much solvent your dose needs
How much solvent you add sets the concentration, so this decides your dose. Using the full 10 mL gives a solution of 1,000 units per mL — at that strength a 10,000-unit dose is 10 mL and a 5,000-unit dose is 5 mL. Your prescription tells you which. Anything between 1 and 10 mL of the supplied solvent may be used.
Pharmacist tip: If the numbers on your prescription do not match what you are holding, call us at (905) 235 8820 before you mix anything.
- 3
Mix
Equalise the pressure, then transfer
Attach the mixing needle to the syringe. Withdraw sterile air from the powder vial and inject it into the solvent vial first — this equalises the pressure and makes the solvent draw up cleanly. Then withdraw your measured amount of solvent from that vial.
- 4
Mix
Reconstitute the powder
Add the solvent to the vial of powder and agitate gently until the powder has dissolved completely. Do not shake it vigorously. Then look at what you have: the powder should have been a white dry cake and the solvent clear and colourless. If the mixed solution is discoloured or has particles floating in it, do not use it.
- 5
Mix
Draw your dose and change needles
Draw up your prescribed volume, then remove the mixing needle and attach the intramuscular injection needle. Hold the syringe upright, tap it so any bubbles rise, and press the plunger gently until a drop appears at the needle tip. Never mix Pregnyl® in the same syringe or vial with any other medicine.
- 6
Inject
Clean the site
This injection goes into a large muscle, usually the upper outer buttock, and someone else gives it — you cannot see or reach the site properly yourself. Clean about a two-inch area with an alcohol pad and let it dry for a full minute.
- 7
Inject
Give the intramuscular injection
Shift your weight onto the opposite leg so the muscle relaxes. Your partner stretches the skin taut, holds the syringe like a dart about three inches from the skin at a 90° angle, and inserts the whole needle in one smooth motion. They pull back slightly on the plunger first — if blood appears, they withdraw, discard that needle, and start again at a new site. If no blood appears, they inject slowly and steadily until the syringe is empty, then withdraw quickly.
- 8
After
After the injection
Apply firm pressure with gauze or an alcohol pad until any bleeding stops, then massage the area gently to help the medication absorb. Put the syringe and needles straight into a hard sharps container without recapping. If you have solution left in the vial and will use it again, refrigerate it at 2–8°C — never freeze it — and discard whatever remains once you no longer need it.
What to expect
Side effects to know about
Common, usually mild
- Reactions where the needle went in: bruising, pain, redness, swelling and itching
- Headache
Rare, but serious
- Ovarian hyperstimulation syndrome (OHSS): mild to moderate causes abdominal pain, nausea, diarrhoea and enlarged ovaries — watch for at least two weeks after the injection
- Severe OHSS can be life-threatening: acute abdominal pain, shortness of breath, reduced urine output or weight gain means urgent medical attention
- Pain and/or a rash at the injection site can signal an allergic reaction
- The supplied solvent contains benzyl alcohol as a preservative
Common questions
Pregnyl (hCG)® FAQ
Something not covered here? Call (905) 235 8820 and a pharmacist will walk you through it.
Is this injected into muscle or under the skin?
Into muscle. The Canadian product monograph for Pregnyl® states it is for intramuscular use only after reconstitution, and Health Canada lists intramuscular as the sole authorised route. If you have been dispensed a different chorionic gonadotropin product, follow the leaflet that came with it and your clinic’s instruction — and if anything you have been told differs from this page, follow your clinic and call us at (905) 235 8820.
Can I inject it myself?
Not practically. An intramuscular dose into the upper outer buttock needs a trained partner, caregiver or healthcare provider, because you cannot see or reach the site properly. If nobody at home can do it, tell your clinic — that is a common situation and they will arrange it.
How long does the mixed solution keep?
Unmixed vials are stored at room temperature, 15°C to 30°C. Once reconstituted, the solution keeps for 28 days if refrigerated at 2°C to 8°C. Never freeze it, and discard any leftover once you no longer need it.
How soon does it start working?
Blood levels rise within about two hours of the injection and peak by around six hours. That is why your clinic specifies the hour and not just the day.
What if I inject at the wrong time, or miss the dose?
Contact your fertility specialist immediately. Timing is critical for a trigger shot, and injecting too early or too late can affect the cycle. Do not give extra doses to compensate unless you are specifically told to — sticking to the prescribed dose and schedule matters, because OHSS can be triggered by this injection.
Why did my pregnancy test come back positive so soon?
Pregnyl® can interfere with hCG testing for up to ten days after the injection, giving a false positive on a home pregnancy test. Wait for the blood test your clinic schedules rather than testing early — an early positive here usually means the medication, not a pregnancy.
What should I watch for after the trigger?
Keep an eye out for ovarian hyperstimulation syndrome for at least two weeks. Early OHSS usually appears within 10 days of the injection. Mild to moderate OHSS causes abdominal pain, nausea, diarrhoea and enlarged ovaries. Severe OHSS can be life-threatening — acute abdominal pain, shortness of breath, reduced urine output, or weight gain means contact your clinic or seek urgent care right away.
Can I reuse a syringe or needle?
No. Both are strictly single-use. Reusing them raises the risk of infection and makes the injection more painful.
Where this comes from
Checked against the official record
Every clinical statement on this page was checked against the sources below, then reviewed by our pharmacist. If something here does not match what your clinic told you, follow your clinic and call us.
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We dispense it the same day your clinic sends the prescription, deliver across the GTA, and counsel you through your first injection.