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Fertility Medications: Types, How They Work, Side Effects & Safety
Fertility medications help many people conceive — most often by encouraging the ovaries to release an egg (ovulation induction).
Quick Facts
Fertility medications help many people conceive — most often by encouraging the ovaries to release an egg (ovulation induction) in those who don't ovulate regularly, such as women with PCOS. They're also used as part of IUI and IVF cycles.
The most common options are the oral medicines clomifene (clomifene citrate) and letrozole, with gonadotropin injections (FSH-based) used in some cases, and metformin sometimes added for insulin-related issues in PCOS. These medicines are effective but must be prescribed and monitored by a specialist, because they carry real risks — chiefly multiple pregnancy and ovarian hyperstimulation syndrome (OHSS) — that need careful management.
This page is an educational overview of what each medicine does, what it's used for, common side effects, and the safety essentials — not a guide to doses or self-treatment. Your specialist will choose and monitor any medicine for your situation. For the conditions behind their use, see Female Fertility and PCOS.
Never buy or take fertility medicines without a doctor
All fertility medicines are prescription-only and specialist-monitored. Self-medicating is dangerous — risks include dangerous ovarian over-stimulation and high-order multiple pregnancy. Never obtain or use these medicines without medical supervision.
Useful tools
Things worth knowing
They mostly help you ovulate
Ovulation induction encourages the ovaries to release an egg in those who don't ovulate regularly.
Letrozole and clomifene are oral
These two pills are the common first options for ovulation problems, especially in PCOS.
Gonadotropins are injectable
FSH-based injections directly stimulate the ovaries when oral agents don't work, and in IVF.
Higher chance of twins
Fertility drugs raise the chance of multiple pregnancy, which is why monitoring matters.
OHSS is the key risk
Ovarian hyperstimulation can cause swollen, painful ovaries; severe cases need urgent care.
Specialist-only, never self-medicate
All fertility medicines are prescription-only and must be selected and monitored by a specialist.
Everything You Need to Know (The Main Medicines)
An overview of common fertility medicines — all specialist-prescribed and monitored:
| Medicine | What it is / does | Commonly used for |
|---|---|---|
| Letrozole | An aromatase inhibitor that lowers oestrogen, prompting the body to stimulate egg development | Ovulation induction (often first-line, e.g. in PCOS); evidence suggests higher live-birth rates than clomifene in PCOS |
| Clomifene (clomifene citrate) | A selective oestrogen-receptor modulator that boosts the hormones driving egg growth/release | Ovulation induction; note around 70% don't conceive over a course despite treatment |
| Gonadotropins (FSH/LH injections) | Injectable hormones that directly stimulate the ovaries | When oral agents don't work, and in IUI/IVF cycles; needs close monitoring |
| Metformin | Improves insulin sensitivity | Sometimes added in PCOS with insulin resistance — see PCOS |
| Trigger injection (hCG) | Triggers final egg maturation/release | Times ovulation in IUI/IVF |
Letrozole vs clomifene
For ovulation problems (especially PCOS), trials and meta-analysis suggest letrozole leads to more live births than clomifene — your specialist will decide what suits you.
Reassuring safety point
The risk of birth defects with clomifene and letrozole appears low and comparable to natural conception.
Side Effects
Most people tolerate these medicines well, but side effects can include:
Oral agents (clomifene/letrozole)
- Hot flushes, headaches, nausea
- Breast tenderness, bloating, fluid retention
- Mood changes; (clomifene) occasional visual disturbance — report this
Gonadotropins
- Injection-site reactions, bloating, ovary tenderness
- Higher need for monitoring due to OHSS and multiple-pregnancy risk
Metformin
- Tummy upset, nausea (often eases over time)
Track while you read
Tick the symptoms that apply to you. This is a self-check, not a diagnosis — saved on this device only.
Report urgently (possible OHSS)
Severe abdominal pain/swelling, rapid weight gain, severe nausea/vomiting, breathlessness, or reduced urination — contact your clinic the same day.
Why Fertility Medicines Are Used
They address specific problems:
- Anovulation / irregular ovulation
- E.g. PCOS — the most common reason for ovulation induction.
- Unexplained infertility
- Often with IUI.
- As part of IUI
- To stimulate and time ovulation.
- As part of IVF
- Gonadotropins stimulate multiple eggs for retrieval.
- Insulin resistance in PCOS
- Metformin in selected cases.
Assessment Before Medicines
A specialist confirms the cause and checks suitability before prescribing.
Assessment includes
- Confirming ovulation status and the cause (e.g. PCOS, thyroid, prolactin) — see Fertility Testing
- Baseline scans/blood tests and checking the fallopian tubes/uterus where relevant
- A partner's semen analysis — fertility is a couple's matter
- A monitoring plan — scans and blood tests during treatment to track response and reduce risks
How They're Used (With Monitoring)
Medicines are used in carefully monitored cycles. Dosing is individualised, adjusted to your response, and never provided here.
- Ovulation problems (e.g. PCOS)
- Oral agent (often letrozole) for a number of cycles, with scan monitoring.
- Oral agents not working
- Gonadotropin injections, with close monitoring.
- IUI
- Stimulation +/- trigger, timed to insemination.
- IVF
- Gonadotropins to grow multiple eggs, then trigger and retrieval.
- PCOS + insulin resistance
- Metformin may be added.
Follow your plan safely
Use Ask a Doctor on ParentVibes for general guidance (not emergencies) to help you follow your clinic's plan.
Ask a Doctor →Monitoring is essential
Monitoring limits multiple pregnancy and OHSS — which is why these medicines are never safe to use without specialist supervision. All fertility medicines are prescription-only; never self-medicate. This page does not provide doses.
Using Medicines Safely
If you're prescribed fertility medicines:
Using your medicines safely
- Follow the exact schedule your clinic gives you; set reminders
- Attend every monitoring appointment — these keep you safe
- Learn injection technique properly (for gonadotropins) from your clinic
- Store medicines correctly (some need refrigeration)
- Know the OHSS warning signs and your clinic's emergency contact
- Support your body — balanced diet, hydration, gentle activity, and emotional support — see Emotional Support
Medication-safety checklist
- Reminders set
- Monitoring booked
- Injection technique learned (if relevant)
- Correct storage
- OHSS signs & clinic contact known
When to See a Doctor
Contact your clinic/doctor:
- Urgently for OHSS warning signs (severe abdominal pain/swelling, rapid weight gain, severe vomiting, breathlessness, reduced urination)
- For visual disturbance on clomifene
- For side effects that worry you, or if you miss a dose
- To review the plan after a cycle
- Before taking any other medicine or supplement alongside fertility drugs
OHSS can become serious
Seek same-day care for the warning signs above. Use Ask a Doctor on ParentVibes for general guidance (not emergencies).
Continue learning
Frequently Asked Questions
What are the most common fertility medications?
Oral agents clomifene and letrozole (for ovulation induction), gonadotropin injections (in some cases and for IVF), and metformin (for insulin-related PCOS). All are specialist-prescribed and monitored.
Is letrozole or clomifene better?
For ovulation problems, especially PCOS, evidence suggests letrozole leads to more live births than clomifene — but your specialist decides based on you.
Do fertility drugs cause twins?
They raise the chance of multiple pregnancy (often quoted around 5-10% for oral agents, higher with gonadotropins), which is why monitoring matters.
What is OHSS?
Ovarian hyperstimulation syndrome — an over-response to fertility medicines causing swollen, painful ovaries; severe cases need urgent care. Monitoring reduces the risk.
Are fertility medicines safe for the baby?
The risk of birth defects with clomifene and letrozole appears low and similar to natural conception.
Can I buy fertility medicines online?
No — they are prescription-only and must be prescribed and monitored by a specialist; self-use is dangerous.
What are common side effects?
Hot flushes, headaches, nausea, bloating and mood changes; most people tolerate them well. Report visual changes (clomifene) and OHSS signs.
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Medical review
- Last reviewed
- June 2026
- Medical reviewer
- Dr. Vinika G.
- Next review due
- June 2027
- Status
- Medically reviewed by Dr. Vinika G.
References
- NHS — Infertility (Treatment)
- NHS (Gloucestershire Hospitals) — Ovulation induction with oral agents (Clomid and Letrozole)
- Letrozole at the Crossroads of Efficacy and Fetal Safety in Ovulation Induction: A Narrative Review (PMC)
- The Success of Ovulation Induction with Letrozole and Gonadotropins (PMC)
This article is for general information and education only and is not a substitute for professional medical advice, and not a dosing or self-treatment guide. Fertility medicines are prescription-only and must be selected, dosed and monitored by a qualified fertility specialist; misuse can cause serious harm. Never obtain or take these medicines without medical supervision. Seek urgent care for OHSS warning signs. In a medical emergency, contact your clinic or local emergency services immediately. Content reviewed against guidance from the NHS and peer-reviewed literature.
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Medical disclaimer
This article is for educational purposes only and does not replace medical advice. If you have severe pain, heavy bleeding, missed periods, or unusual symptoms, please consult a qualified healthcare provider.