Progesterone Suppositories vs Pills vs Injections

You have been told to take progesterone after your ovulation induction cycle, your IUI, or your embryo transfer, and your clinic has either given you a route or asked which one you would prefer. Each option, vaginal, intramuscular (IM), and oral, has a different mechanism, a different daily experience, and a different evidence base. None is universally better; the right choice depends on the protocol, the goal, and your tolerance.

This post walks through what each route does inside the body, what the daily reality looks like, what the outcome data says when routes are compared head to head, and what to ask your reproductive endocrinologist (RE) if a route is not working for you.

Why the route matters more than you might think

Progesterone behaves very differently depending on how it enters the body, because of where it goes first and how the liver metabolises it.

• Vaginal progesterone passes through the first uterine pass effect, where venous drainage from the vagina concentrates progesterone in the uterus before it reaches the general circulation.⁶ The result is high uterine concentration with relatively lower blood levels, which can be confusing if you have a serum progesterone drawn on vaginal supplementation.
• Intramuscular progesterone in oil (PIO) goes into muscle tissue, releases slowly over 24 hours, and produces high and stable blood levels that reach the uterus through the bloodstream like any other circulating hormone.
• Oral micronized progesterone is absorbed through the gut, hits the liver in first-pass metabolism, and is partially broken down before reaching the uterus. The result is decent blood levels but lower uterine effect compared with the other routes, and noticeable systemic side effects (drowsiness, dizziness) from neuroactive metabolites.

This is why a Cochrane meta-analysis of luteal phase support in ART cycles concluded that vaginal and intramuscular routes are roughly equivalent for live birth rates, while oral progesterone (as monotherapy) lags behind in IVF settings.¹

Vaginal progesterone, the workhorse route

Vaginal preparations are the most common in fertility medicine outside of full IVF cycles. They come in three main forms.

Crinone gel (vaginal progesterone gel, 8% or 4%) is a sustained-release gel applied with an applicator, usually once or twice daily. Pro: pre-dosed, no mess once inserted, well-tolerated. Con: expensive without insurance, can leave white residue.

Endometrin (vaginal progesterone tablets, 100mg) is a small effervescent tablet inserted with an applicator two or three times daily. Pro: no oil, less mess than gel, evidence-supported. Con: residue, multiple daily doses.

Compounded vaginal suppositories are prepared at a compounding pharmacy in various strengths (often 100mg or 200mg) and inserted manually two or three times daily. Pro: cheapest, customisable dose. Con: more mess, depending on the base used (cocoa butter vs polyethylene glycol).

The daily experience of vaginal progesterone:

• Discharge: effectively guaranteed. Most patients use panty liners for the duration of supplementation. The discharge is often white or yellow, sometimes slightly tinged, and can be mistaken for pre-period spotting.
• Bedtime dosing reduces leakage: lying down for 15 to 30 minutes after insertion lets the medication absorb and minimises immediate fall-out.
• Timing: twice or three times daily, spaced as evenly as the schedule allows.
• Not for use during sex: a few hours' gap is fine, but going straight from insertion to intercourse is not effective for either purpose.

Best fit for: standard IUI luteal support, IVF transfer cycles, post-trigger luteal support in oral medication cycles.

Intramuscular progesterone (progesterone in oil)

PIO is the original luteal support preparation and still the standard in many IVF programs in the United States.

Progesterone in oil (PIO), typically 50mg/mL is administered as a deep intramuscular injection, usually into the upper outer quadrant of the buttock, once daily. The carrier oil is most often sesame oil; ethyl oleate or olive oil are alternatives for those with sesame allergy.

The daily experience of PIO:

• The needle: usually a 22-gauge, 1.5-inch needle. Most patients prefer to have a partner or a friend administer it, because the angle and depth on the buttock are awkward to self-administer.
• The oil is thick: warming the syringe in your hand or against your body for a few minutes before injection makes the oil flow better and reduces injection time.
• Site rotation: alternate between left and right upper outer glute. Some patients use a small dot of marker on the skin to track the day's site.
• Lumps and bruises: common with weeks of daily injections. Massaging the site after the injection and using a heat pack later helps. Some patients develop persistent lumps that take months to resolve after discontinuation.
• Allergic reactions: rare but documented, more commonly to sesame oil than to progesterone itself. Switching to an ethyl oleate-based PIO usually resolves the issue.

Outcome data for PIO in IVF: the Devine trial specifically compared vitrified embryo transfer cycles using vaginal-only progesterone (Endometrin) versus those including IM progesterone, and found inferior ongoing pregnancy rates with vaginal-only support in that setting.² The result is one of the reasons many US IVF programs continue to use PIO, often in combination with vaginal preparations, for frozen embryo transfers.

Best fit for: IVF fresh and frozen transfer cycles, clinics that prefer PIO protocols, patients who cannot tolerate vaginal preparations.

Oral micronized progesterone

Oral micronized progesterone (Prometrium, Utrogestan) comes in 100mg or 200mg capsules and is taken once or twice daily, usually at bedtime.

The daily experience:

• Drowsiness: the hallmark side effect, sometimes pronounced. The metabolites of oral progesterone have a sedative effect, which is why bedtime dosing is standard.
• Dizziness: especially in the first few days. Improves with continued use.
• Mood changes: variable. Some patients feel calm; others feel low.
• Convenience: no needles, no discharge. The most discreet route.
• Less effective for uterine effect: first-pass liver metabolism reduces the uterine concentration significantly compared with vaginal or IM routes.

Comparative data on oral progesterone is mixed. The Tomic trial in 2015 compared oral dydrogesterone (a related compound used outside the US) with vaginal progesterone gel and found roughly comparable outcomes in ART cycles.⁴ The more general oral micronized progesterone preparation has weaker evidence for ART use as a sole agent.

Best fit for: shorter-term use, supplementation in natural cycles, patients who cannot tolerate vaginal or IM preparations, some early-pregnancy continuation protocols.

How progesterone routes compare for outcomes

The summary table I would write on a clinic whiteboard:

Setting	Vaginal	IM (PIO)	Oral micronized
IVF fresh transfer	Standard	Standard, possibly better in some protocols2	Inferior as monotherapy
IVF frozen transfer	Common, sometimes with IM	Common, especially in US programs	Not preferred as sole agent
IUI luteal support	First-line	Rare	Sometimes used
Ovulation induction with trigger	First-line	Rare	Reasonable, less common
Natural cycle supplementation	Often used	Rare	Common, well-tolerated

The Cochrane review remains the cleanest summary: in ART cycles, vaginal and IM are roughly equivalent for the headline live-birth outcome, with route-specific tradeoffs in patient experience.¹ The Polyzos meta-analysis of vaginal gel specifically also supports its use in IVF luteal support.³

Cost comparison

US-specific, varies widely by insurance.

• Crinone gel: $$$. Often $300+ per cycle uninsured.
• Endometrin tablets: $$. Often $150 to $300 per cycle uninsured.
• Compounded vaginal suppositories: $. Often $30 to $80 per cycle.
• PIO injection: $ to $$. Varies by pharmacy; compounded PIO is often $50 to $150 per cycle.
• Oral Prometrium: $ to $$. Often $30 to $100 per cycle as a generic.

If the prescription cost is a real issue, ask your clinic whether a compounded vaginal suppository or a different oral preparation would be acceptable. Most clinics have some flexibility, even if the default prescription is for a brand name.

Common side effects by route

A quick reference, grouped by which complaints come from which delivery method.

Vaginal preparations.

• White or yellow discharge (universal).
• Vaginal or vulvar irritation (variable, sometimes route-related to the inactive ingredients).
• Mild burning at insertion (uncommon, often improves).

Intramuscular PIO.

• Injection site pain in the first 24 hours (universal).
• Lumps and bruises at injection sites (common with weeks of use).
• Skin redness or itching (occasional, sometimes from the oil).
• Allergic reactions, rare.

Oral micronized progesterone.

• Drowsiness and dizziness (common, especially in the first few days).
• Mood changes (variable).
• Dry mouth (uncommon).

Universal across all routes.

• Breast tenderness.
• Fatigue.
• Mild mood variability.
• Symptoms that mimic early pregnancy, which is genuinely confusing during the two-week wait.

What to ask your RE about route

If you have flexibility, or if you are not tolerating the route you were given, these are the practical questions.

• Why this route for me, in this protocol.
• Is the choice of route based on clinic preference or on something specific to my situation.
• Is there flexibility if I have side effects I cannot live with.
• Can I switch routes mid-cycle if needed, and how would that change the schedule.
• What is the stop date, and what happens if I stop early on my own.

Switching routes mid-cycle is usually possible but should be coordinated with the clinic. The dose conversions are not perfectly clean across routes, so eyeballing the swap is a bad idea.

Practical tips by route

For vaginal preparations.

• Wear panty liners. Black underwear if the residue is visible through clothes.
• Insert at night when possible, then lie down for 15 to 30 minutes.
• For early-morning insertion, stay in bed for a few minutes before getting up.
• Keep applicators away from heat (a hot car in summer melts gel-based products).

For PIO.

• Warm the syringe in your hand or under your arm for a few minutes before injecting.
• Have your partner inject if possible; the angle on the upper outer buttock is easier from behind.
• Ice the site for a minute before injecting; heat the site for a few minutes after.
• Rotate sites and track them. A small calendar with L/R notation helps.
• If a lump forms, warm compresses and gentle massage usually clear it over days to weeks.

For oral preparations.

• Take with food to reduce dizziness.
• Schedule the largest dose at bedtime.
• Plan for not driving immediately after a dose, especially in the first few days.
• Do not crush or split the capsules unless your clinic instructs you to.

What's next

• If you want the pillar overview of luteal phase progesterone: luteal phase progesterone
• If you are figuring out the timing of progesterone after your trigger: when doctors prescribe progesterone after ovulation induction
• If you are preparing for an embryo transfer: IUI explained
• If this cycle didn't work and you are deciding what comes next: when a cycle doesn't work

Sources

1. van der Linden M, Buckingham K, Farquhar C, Kremer JAM, Metwally M. Luteal phase support for assisted reproduction cycles. Cochrane Database of Systematic Reviews 2015;(7):CD009154. https://doi.org/10.1002/14651858.CD009154.pub3
2. Devine K, Richter KS, Widra EA, McKeeby JL. Vitrified blastocyst transfer cycles with the use of only vaginal progesterone replacement with Endometrin have inferior ongoing pregnancy rates: results from the planned interim analysis of a three-arm randomized controlled noninferiority trial. Fertility and Sterility 2018;109(2):266-275. https://doi.org/10.1016/j.fertnstert.2017.11.004
3. Polyzos NP, Messini CI, Papanikolaou EG, et al. Vaginal progesterone gel for luteal phase support in IVF/ICSI cycles: a meta-analysis. Fertility and Sterility 2010;94(6):2083-2087. https://doi.org/10.1016/j.fertnstert.2009.12.058
4. Tomic V, Tomic J, Klaic DZ, Kasum M, Kuna K. Oral dydrogesterone versus vaginal progesterone gel in the luteal phase support: randomized controlled trial. European Journal of Obstetrics & Gynecology and Reproductive Biology 2015;186:49-53. https://doi.org/10.1016/j.ejogrb.2014.11.002
5. Practice Committee of the American Society for Reproductive Medicine. Current clinical irrelevance of luteal phase deficiency: a committee opinion. Fertility and Sterility 2015;103(4):e27-e32. https://doi.org/10.1016/j.fertnstert.2014.12.128
6. de Ziegler D, Bulletti C, De Monstier B, Jääskeläinen AS. The first uterine pass effect. Annals of the New York Academy of Sciences 1997;828:291-299. https://doi.org/10.1111/j.1749-6632.1997.tb48550.x