When people start exploring fertility treatment, IUI (intrauterine insemination) and IVF (in vitro fertilisation) are the two treatments they encounter most. The question of which to pursue — or whether to go straight to IVF — depends on diagnosis, age, how long you have been trying, and the evidence for each treatment in your specific situation.

This guide gives an honest comparative overview.

What Is IUI?

IUI involves placing washed, prepared sperm directly into the uterine cavity at or just before ovulation. The goal is to reduce the distance sperm must travel and increase the concentration of motile sperm at the site of fertilisation.

Most IUI cycles in the UK are "stimulated" — the woman takes mild stimulation medication (clomifene tablets or low-dose gonadotrophins) to produce one or two follicles, timed to maximise the chance of ovulation during the insemination window. Natural cycle IUI (no medication) is also possible but has lower success rates.

What Is IVF?

IVF involves stimulating the ovaries with higher-dose hormone injections to produce multiple eggs, retrieving the eggs under sedation, fertilising them in the laboratory, and transferring one or more resulting embryos to the uterus. The key difference from IUI is that fertilisation occurs outside the body, under controlled laboratory conditions, and the embryo (not just the sperm) is introduced into the uterus.

For a full description of the IVF process, see IVF timeline: week by week.

Success Rates Compared

| Treatment | Live birth rate per cycle | |---|---| | Stimulated IUI (all diagnoses) | 8–15% | | IVF under 35 | 30–40% | | IVF 35–37 | 25–30% | | IVF 38–39 | 18–22% | | IVF 40–42 | 10–14% |

The per-cycle success rate of IVF is substantially higher than IUI across all age groups. However, IUI is cheaper and less invasive — so the question is whether the cost and complexity of IVF is justified given your specific situation, or whether multiple IUI cycles is a reasonable first step.

When IUI Is More Appropriate

Donor sperm treatment. For single women, same-sex female couples, or couples using donor sperm, IUI is often the first-line treatment. Where the female partner has no identified fertility problem, multiple IUI cycles with donor sperm carry reasonable cumulative success rates and are significantly cheaper than IVF.

Mild male factor infertility. Where semen analysis shows borderline count or motility (rather than severe male factor), stimulated IUI can improve the chance of conception by concentrating the sperm and placing them closer to the egg. For severe male factor, IUI is unlikely to be effective and IVF with ICSI is recommended directly.

Cervical factor. Where mucus or cervical anatomy makes it difficult for sperm to pass through naturally, IUI bypasses this barrier effectively.

Ovulatory dysfunction with mild stimulation. For patients who ovulate irregularly, stimulated IUI can be an effective treatment, though IVF is also appropriate after failed IUI cycles.

When IVF Is More Appropriate

Tubal factor. If one or both fallopian tubes are blocked or significantly damaged, natural conception and IUI are both unlikely to work — fertilisation in the tube cannot occur. IVF entirely bypasses the tubes.

Severe male factor. Where sperm count is very low, motility is severely impaired, or surgical sperm retrieval is required, IVF with ICSI is the appropriate treatment. IUI requires a functional population of motile sperm capable of reaching the egg.

Age and time pressure. For women over 37, IUI's lower per-cycle success rate means that the cumulative time and cost of multiple IUI cycles may make it less efficient than proceeding directly to IVF. Time spent on IUI cycles that are unlikely to succeed is time during which egg quality continues to decline. See IVF after 40 for more on age and treatment decisions.

After IUI failure. NICE guidance recommends up to 6 IUI cycles before IVF. In practice, many clinics and patients choose to move to IVF after 3 failed IUI cycles, since the incremental value of additional IUI cycles drops as the number increases.

Unexplained infertility with time pressure. For unexplained infertility in patients under 35 with plenty of time, IUI is a reasonable first step. For patients over 37, or those who have been trying for several years, the evidence increasingly favours moving to IVF earlier. See unexplained infertility for more detail.

Cost Comparison

| | IUI | IVF | |---|---|---| | Clinic fee | £500–£1,000 | £3,500–£6,000 | | Medication | £100–£500 | £500–£1,500 | | Monitoring scans | included–£200 | included–£400 | | Total per cycle | £600–£1,500 | £4,500–£8,000 |

IUI is typically 5–8x cheaper per cycle than IVF. However, because IUI has a lower per-cycle success rate, the cost-per-live-birth across multiple IUI cycles may be closer to (or exceed) a single IVF cycle, particularly for patients over 35.

For NHS patients, many ICBs now fund IVF directly without requiring IUI first, based on evidence of IVF's superior cost-effectiveness per live birth. Check what your ICB commissions at nestie.co/nhs.

Invasiveness and Experience

IUI involves an injection protocol (if stimulated) and a clinic procedure similar to a smear test — speculum placement and a fine catheter through the cervix. Most patients find it significantly less demanding than IVF.

IVF involves 10–14 days of daily injections, multiple clinic visits for monitoring scans, an egg collection under sedation (which has a recovery period), and an embryo transfer. The physical and emotional demands are substantially greater.

This difference matters. For patients for whom IVF is medically the more efficient choice, the greater burden is justified. For patients for whom IUI is clinically appropriate, the lower burden and cost of IUI is a genuine advantage.

Frequently Asked Questions

Q: Should I try IUI first, or go straight to IVF?

A: The right answer depends on your diagnosis, age, and how long you have been trying. For donor sperm treatment, cervical factor, or mild male factor, IUI is a reasonable first step. For blocked tubes, severe male factor, or women over 38, IVF is typically the more efficient choice. A fertility specialist can advise based on your specific profile.

Q: How many IUI cycles should I try before moving to IVF?

A: NICE guidance recommends up to 6 stimulated IUI cycles for unexplained infertility or mild male factor. Many clinics and patients move to IVF after 3 failed cycles, particularly if age is a factor. The fourth, fifth, and sixth IUI cycles have lower marginal success rates than the first three.

Q: Is IUI painful?

A: Most patients describe IUI as similar to a smear test — mild cramping or discomfort during the cervical catheter insertion, which usually resolves quickly. Some patients experience cramping for a few hours afterwards. It is performed without anaesthetic.

Q: Does IUI work if I have PCOS?

A: Stimulated IUI can be effective for PCOS patients who are not ovulating regularly, as the stimulation component induces ovulation. Success rates are reasonable for this indication. However, PCOS patients are also at risk of over-response to stimulation, which increases multiple pregnancy risk with IUI (because unlike IVF, you cannot control how many embryos are transferred). Close monitoring during the stimulation phase is important.

Q: Can I use IUI with my own partner's sperm if his count is low?

A: IUI can be used with partner sperm where counts are mildly below normal — the washing and preparation process concentrates motile sperm. Most clinics require a minimum total motile sperm count after preparation (often 5–10 million) to proceed with IUI. Below that threshold, IVF with ICSI is typically recommended instead.

This article is for information only and does not constitute medical advice. Treatment decisions should be made in consultation with a qualified fertility specialist.