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IVF vs IUI: What Is the Difference?

IUI places sperm in the womb so fertilisation happens in the body; IVF fertilises eggs in a lab. IUI is simpler but succeeds about a third as often per cycle.

By Vireon Medical Editorial TeamFirst published Evidence checked through

Short answer

In IUI (intrauterine insemination), prepared sperm are placed directly into the womb around ovulation and fertilisation happens inside the body; in IVF (in vitro fertilisation), eggs are collected and fertilised in a laboratory, and an embryo is then transferred to the womb.12 IUI is simpler and involves fewer drugs, but its success rates are generally around a third of those for IVF.2 Which is more appropriate depends mainly on the reason for treatment: IUI mostly suits people who need donor sperm or cannot have vaginal sex and have no fertility problem, while IVF is usually recommended for problems such as blocked tubes or low sperm quality.1

Key points

  • IUI takes under 10 minutes and does not need egg collection.1
  • IVF lets the clinic see fertilisation and choose embryos; IUI does not.2
  • NICE advises against IUI for unexplained infertility, so the NHS generally does not fund it for that reason.2
  • IUI is unlikely to help with blocked tubes, endometriosis or low sperm quality.1
  • Multiple pregnancy is the main risk when fertility drugs are used with either treatment.23

How the two treatments differ

FeatureIUIIVF
Where fertilisation happensInside the bodyIn the laboratory
Fertility medicinesOptional; NHS IUI usually uses noneUsually 2 to 3 weeks of injections or nasal spray, then about 2 weeks of stimulation injections
Egg collectionNot neededNeedle through the vagina, about 20 minutes, with sedation offered
The procedure itselfSperm passed into the womb through a thin catheter, usually under 10 minutesEmbryo transferred through a thin tube a few days after fertilisation
Typical cycle lengthTimed around one ovulationAbout 3 to 6 weeks
Relative successAround a third of IVF per cycleHigher per cycle
Sources: NHS website; HFEA.

For IUI, the timing of ovulation is found with blood or urine tests, usually 12 to 16 days before the next period is due. If ovulation medicines are used, scans and a hormone injection to release the egg are added.1 IVF follows a longer sequence of medicines, monitoring, egg collection, laboratory fertilisation and embryo transfer, with a pregnancy test about 16 days later.3

The Human Fertilisation and Embryology Authority (HFEA), the UK fertility regulator, summarises the trade-off: IUI lets the body do more on its own, making it a more natural but less successful treatment, whereas IVF lets the clinic check fertilisation and select embryos.2

Who each treatment may suit

According to the NHS and HFEA, IUI may be considered for:12

  • single women and same-sex couples using donor sperm, when there is no known female fertility problem
  • couples who cannot have, or find it very difficult to have, vaginal intercourse
  • people who need sperm washing to reduce the risk of passing on an infection such as HIV.

IVF is usually recommended instead when there are blocked fallopian tubes, endometriosis (womb-like tissue growing outside the womb), low or poor-quality sperm, or poor egg quality or numbers.12 The HFEA also notes that women in their late 30s or over 40 may be advised to try IVF rather than IUI.2

What the success rates look like

The HFEA states that IUI success rates are generally around a third of those for IVF, and that many people need several cycles.2 The NHS gives a cumulative picture: over half of women under 40 using IUI become pregnant within 6 cycles, and about half of the rest become pregnant within a further 6.1

For comparison, UK figures for 2022 show IVF birth rates per embryo transferred of about 35% for women under 35, falling with age.5 These numbers are not directly comparable, because they are measured differently and the people choosing each treatment differ. Overall, the evidence that IVF has a higher success rate per cycle is Moderate, but per-cycle success is only one part of the decision.

How they fit together on the NHS

IUI is not routinely offered on the NHS, and eligibility may depend on age and location.1 NICE criteria for NHS-funded IVF include people with unexplained fertility problems who have not conceived after 2 years of regular unprotected intercourse, and people who have not conceived after 12 cycles of artificial insemination, at least 6 of them IUI.4 For some people, then, IUI comes first and IVF follows if it does not work.

Risks of each

IUI without fertility drugs carries few risks; infection is possible but very rare.1 When ovulation medicines are used, there is a small risk of multiple pregnancy, ectopic pregnancy (a pregnancy outside the womb) and ovarian hyperstimulation syndrome (OHSS, an over-reaction of the ovaries to fertility drugs).1 The HFEA describes multiple pregnancy as the main risk, and clinics may cancel an IUI cycle if too many follicles develop.2 IVF carries the same three risks.3

When to seek medical advice

During or after fertility treatment, the NHS advises contacting the clinic or NHS 111 urgently for tummy pain or bloating, feeling sick, or feeling faint. Call 999 or go to A&E for difficulty breathing, chest or upper back pain, severe thirst with passing little urine, or body swelling.13

Common questions

Is IUI a cheaper, gentler version of IVF?

It is less invasive and uses fewer drugs, but the HFEA warns it is not a substitute for IVF when there is a significant fertility problem.2

Does IUI help with unexplained infertility?

It can be used, but NICE guidance advises against it, and the NHS states it is not likely to help in this situation.12

Can donor sperm be used with either treatment?

Yes. Donor sperm must come through a licensed clinic, where it is frozen and screened, a process that can take up to 6 months.1

Does IUI hurt?

It may cause mild cramping. A speculum is placed in the vagina and a thin catheter passed into the womb, and the procedure usually takes under 10 minutes.1

Bottom line

IUI is a simpler treatment that places sperm close to the egg and leaves fertilisation to the body; IVF takes fertilisation into the laboratory and has higher success per cycle. The choice depends less on preference than on the cause of the fertility problem, age and access.

Sources

  1. NHS. Intrauterine insemination (IUI). NHS website; 2024. https://www.nhs.uk/tests-and-treatments/intrauterine-insemination-iui/. Accessed 5 November 2026.
  2. Human Fertilisation and Embryology Authority (HFEA). Intrauterine insemination (IUI). HFEA; 2016. https://www.hfea.gov.uk/treatments/explore-all-treatments/intrauterine-insemination-iui/. Accessed 5 November 2026.
  3. NHS. IVF. NHS website; 2025. https://www.nhs.uk/tests-and-treatments/ivf/. Accessed 5 November 2026.
  4. National Institute for Health and Care Excellence (NICE). Fertility problems: access criteria for in vitro fertilisation (IVF). NICE guideline NG257. https://www.nice.org.uk/guidance/NG257/chapter/access-criteria-for-in-vitro-fertilisation-ivf. Accessed 5 November 2026.
  5. Human Fertilisation and Embryology Authority (HFEA). Fertility treatment 2022: preliminary trends and figures. HFEA; 2024. https://www.hfea.gov.uk/about-us/publications/research-and-data/fertility-treatment-2022-preliminary-trends-and-figures/. Accessed 5 November 2026.

Article history

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