IUI (intrauterine insemination): what it involves and what to expect

Trying to conceive · Updated July 2026 · All articles

What IUI is and what it is not

Intrauterine insemination (IUI) is a fertility treatment in which washed and concentrated sperm is placed directly into the uterus around the time of ovulation. The goal is to increase the number of sperm that reach the egg, bypassing some of the natural barriers in the cervix and lower reproductive tract. Fertilisation still takes place inside the body, which is what makes IUI fundamentally different from IVF.

IUI is not the same as IVF. It does not involve egg collection, laboratory fertilisation or embryo transfer. No eggs are retrieved; no surgery is required. IUI is a much simpler, less expensive and less physically demanding procedure than IVF, with correspondingly more modest per-cycle success rates.

Understanding this distinction matters because people sometimes arrive at IUI expecting something closer to the controlled environment of IVF, and the simplicity of the actual procedure can be surprising. The trade-off is that IUI requires sperm and egg to find each other naturally once the sperm is in the uterus, which means it works best when the main barrier being addressed is getting sperm closer to the egg rather than a more fundamental problem with fertilisation or embryo development.

Who is IUI most likely to help?

IUI is most effective in a defined set of circumstances. Mild male factor infertility, where sperm count or motility is slightly below normal but not severely reduced, is one of the clearest indications. Placing washed, concentrated sperm higher in the reproductive tract increases the odds of enough sperm reaching the egg despite the lower baseline numbers.

Cervical factor infertility, where the cervical mucus is hostile to sperm or physically obstructive, is another indication. Bypassing the cervix entirely with a catheter addresses this barrier directly. IUI is also used for unexplained infertility as a first-line treatment before proceeding to IVF, and it is the standard approach for people using donor sperm, including same-sex couples and single people by choice.

IUI is not appropriate in all circumstances. If both fallopian tubes are blocked, sperm cannot travel from the uterus to the egg regardless of how it was placed there; IVF is needed in this case. If sperm counts are severely low or there is a significant sperm morphology problem, IUI is unlikely to achieve much improvement and IVF with ICSI is usually recommended instead.

Natural versus stimulated IUI

IUI can be done in a natural cycle, tracking ovulation and timing the insemination around the natural LH surge, or in a stimulated cycle where low-dose medication (typically clomiphene citrate or injectable gonadotrophins) is given to encourage one or two follicles to develop. The insemination then follows a trigger injection of hCG to time ovulation precisely.

Stimulated IUI has a modestly higher per-cycle success rate than natural IUI, largely because it allows ovulation to be timed more precisely and may improve the uterine environment. The main risk is multiple pregnancy: if more than one follicle matures and both eggs are fertilised, the result may be twins or triplets. Most clinics aim to cancel or convert a stimulated cycle to timed intercourse if three or more follicles develop, to avoid this risk.

For people using donor sperm or those with mild unexplained infertility and good ovarian reserve, natural IUI is often tried first before stimulated cycles. Stimulated IUI tends to be recommended when natural cycles have been unsuccessful or when timing ovulation naturally is difficult due to cycle irregularity.

The procedure, step by step

On the day of the insemination, a sperm sample is produced (by the partner or from a donor vial) and processed in the laboratory. Washing removes seminal fluid and concentrates the motile sperm into a small volume of nutrient-rich medium. The processing typically takes around one to two hours.

The insemination itself takes only a few minutes. A speculum is inserted (as with a smear test), a fine flexible catheter is passed gently through the cervix into the uterus, and the prepared sperm is injected. Most people describe it as feeling similar to a cervical smear: a brief moment of pressure or mild cramping. There is no anaesthesia, and you can usually leave the clinic shortly afterwards and return to normal activities the same day.

After the procedure, you enter the two-week wait before taking a pregnancy test. Some clinics prescribe progesterone support (pessaries or injections) during the two-week wait to support the luteal phase, particularly in stimulated cycles. If a trigger injection was used to time ovulation, it contains hCG and can cause a false positive on a pregnancy test for around 10 to 14 days after the injection, so waiting the full recommended period before testing avoids a misleading result.

Success rates: what the numbers actually mean

Per-cycle success rates for IUI vary depending on age, diagnosis and whether the cycle was stimulated, but a realistic range for people with unexplained infertility or mild male factor under 35 is around 10 to 15 percent per attempt. This is meaningfully higher than the natural monthly conception rate of approximately 15 to 20 percent in fertile couples, but it is not a dramatic increase.

Cumulative success rates across multiple cycles are more encouraging. Three to four IUI cycles give cumulative success rates of around 30 to 45 percent in suitable candidates. After six cycles, the marginal benefit of further IUI diminishes significantly, and most guidelines recommend moving to IVF at that point if pregnancy has not occurred.

Age has a significant impact on IUI success rates. Rates are meaningfully lower for people over 38, which is one reason fertility specialists often recommend moving to IVF sooner in older age groups rather than spending time on multiple IUI cycles. If you are over 38 and have been advised to try IUI first, it is worth asking your specialist specifically how many cycles they recommend before reassessing.

How many cycles before moving to IVF

Most fertility guidelines recommend three to six IUI cycles before considering a move to IVF, assuming there is no change in circumstances (such as a new test result) that would prompt an earlier decision. Three cycles gives a reasonable opportunity to benefit from IUI while minimising the time spent on a less effective treatment if IVF will ultimately be needed.

Some clinics and guidelines favour moving to IVF sooner, particularly for people over 35 or those with any factors suggesting a less optimal IUI prognosis. The rationale is that time spent on multiple IUI cycles has an opportunity cost, and moving to IVF earlier may be more efficient overall.

This is ultimately a decision to make with your clinical team, based on your age, diagnosis, how you have responded to any stimulation and what you feel emotionally ready for. IUI and IVF are not in competition; they are sequential steps in most people's journeys, and the right pace varies from person to person.

The emotional experience of IUI

IUI cycles tend to feel both less intense and less hopeful than IVF, which can be a strange combination. The procedure is straightforward; there is less monitoring and fewer interventions. But the two-week wait has the same emotional weight as any other cycle, and a failed IUI can be just as difficult to absorb as any other unsuccessful attempt.

Because IUI success rates per cycle are modest, it is common to go through three or four cycles without success before something works or before moving to IVF. This cumulative experience of negative tests is emotionally costly even when each individual cycle was low-intensity. Being realistic about this from the outset, and building in support for yourself during the process, is not pessimism; it is preparation.

If you are doing IUI with donor sperm, there may be additional emotional layers around the donor decision itself: whether to use an anonymous or known donor, what information to keep, and how to think about disclosure to a future child. These are significant questions that are worth working through with support before or alongside treatment rather than putting aside entirely.

What IUI costs

NHS funding for IUI has become more limited in recent years in many parts of England. Some Integrated Care Boards fund IUI for specific indications (such as single people or same-sex couples using donor sperm, or those with certain medical conditions), while others have stopped funding it altogether. It is worth checking your local ICB's current policy.

Privately, natural cycle IUI typically costs between 700 and 1,200 pounds per cycle in the UK, depending on the clinic and what monitoring is included. Stimulated IUI adds the cost of medications, which can range from a few hundred to over 1,000 pounds depending on the protocol. Donor sperm has a separate cost if required, plus storage fees.

Compared to IVF, IUI is considerably less expensive per cycle, which makes it a more accessible starting point for many people. Given its per-cycle success rate, the cumulative cost of three to four IUI cycles before moving to IVF is often lower than the cost of a single IVF cycle, making IUI a reasonable first step even for those who may eventually need IVF.

Frequently asked questions

How is IUI different from IVF?

In IUI, washed sperm is placed directly into the uterus around the time of ovulation, and fertilisation takes place inside the body. In IVF, eggs are retrieved from the ovaries, fertilised in a laboratory, and resulting embryos are transferred back. IUI is less invasive, less expensive and requires no egg collection or anaesthesia.

What is the success rate of IUI per cycle?

Per-cycle success rates are typically 10 to 15 percent for people with unexplained infertility or mild male factor, rising to around 15 to 20 percent with stimulated IUI in some studies. Cumulative success rates across 3 to 6 cycles of 30 to 45 percent are reported in suitable candidates under 35.

Does stimulated IUI improve success rates?

Yes, modestly. Stimulated IUI has slightly higher per-cycle success rates than natural cycle IUI, but the trade-off is a small risk of multiple pregnancy if more than one follicle matures. Most clinics aim for a maximum of two follicles in a stimulated IUI cycle.

Is IUI painful?

The insemination itself is a brief procedure similar to a smear test. Most people feel mild cramping during or just after, which typically passes within minutes. Some feel no discomfort at all. No anaesthesia is needed and you can usually go about your day normally afterwards.

How long is the two-week wait after IUI?

The wait runs from the day of the procedure to around 14 days later, when a pregnancy test is reliably accurate. If an hCG trigger injection was used, testing too early can give a false positive before the hCG clears. Waiting the full period is recommended for a reliable result.

When is IUI not recommended?

IUI is unlikely to be recommended if both fallopian tubes are blocked, if sperm counts are severely low, or if ovarian reserve is very poor. In these situations, IVF is a more appropriate treatment because the barriers to natural-style fertilisation are too significant for IUI to be effective.

This article is for general information only. If you have concerns about your fertility or reproductive health, speak to your GP or a fertility specialist.