Your male partner has a borderline low sperm count or low motility. This is when the sperm’s ability to move is impaired. But there must be enough healthy, motile sperm to make the treatment worthwhile. If not, IVF or ICSI may be more suitable.
You are unable to have sex because of disability, injury, or if your partner experiences premature ejaculation.
You have mild endometriosis.
You or your partner’s fertility problems are unexplained.
If you are a single woman, IUI may seem like a viable option. Using sperm donated through a clinic has a number of advantages over self-insemination at home. 

For IUI to work, your fallopian tubes must be open and healthy. To find this out, you will need to have a tubal patency test. This can be done using laparoscopy, which is a form of keyhole surgery, or a hysterosalpingogram, which is a form of X-ray. These may locate any problems or blockages in your uterus or fallopian tubes. 

IUI isn’t recommended if both your tubes have adhesions or scarring that might stop an egg traveling from the ovary to your uterus. But if you have at least one working tube and ovary on the same side, IUI may be an option for you.

Depending on your particular fertility problem, you may need to use fertility drugs alongside your IUI treatment. If you do take fertility drugs it’s called a stimulated cycle, because the drugs stimulate ovulation. If drugs are not used it’s called an unstimulated cycle, or natural cycle. 

Stimulating ovulation is not recommended if only your partner has a fertility problem, or if the reason for infertility is unexplained. This is because there is a much greater risk of a multiple pregnancy when taking fertility drugs. 

You may think that twins or more would be a great way to start a family if you have fertility problems. But multiple pregnancies increase your risk of miscarriage and other pregnancy complications. 

In unstimulated cycles, IUI is timed to take place at the time of natural ovulation. You may be asked to detect ovulation using an ovulation predictor kit, or your doctor may track your cycle using blood tests and an ultrasound. IUI is usually done between day 12 and day 16 of a natural menstrual cycle, but the exact day will depend on your individual cycle. 

If your fertility specialist has offered IUI during a stimulated cycle, you’ll probably be given fertility drugs in the form of pills or injections. You’ll start taking the drug near the beginning of your menstrual cycle to stimulate your ovaries to develop several mature eggs for fertilization. This is rather than your usual one egg per month. 

An ultrasound helps to locate the egg and check that it is mature. This will allow insemination to take place at the best time. You may ovulate naturally, or be given an injection of a hormone called human chorionic gonadotrophin (hcg) to bring it on. 

Sperm is then inserted into your uterus within 24 hours and 40 hours of the hcg injection, or when you have a rise (surge) in luteinizing hormone (LH). Your partner produces a sperm sample, which is washed to extract the best quality, most mobile sperm. 

Using a catheter (tube) through your cervix, your doctor will then put this sperm directly into your uterus near a fallopian tube. This is the passage the egg travels along from an ovary to your uterus. 

If you have unexplained infertility, the sperm may be inserted within a larger volume of fluid than usual. This allows it to wash up into your fallopian tubes more easily (fallopian sperm perfusion). This technique takes a few minutes more than standard IUI and may increase your chance of success. 

After IUI you will rest for a short time and then carry on life as normal. You’ll be able to take a pregnancy test in about two weeks.

The insemination itself is straightforward and takes only a few minutes. If you are having a stimulated cycle, you’ll need to take fertility drugs before you ovulate.

Success rates depend on the cause and severity of the infertility and your age. Up to six cycles of IUI treatment are recommended for unexplained infertility or mild endometriosis, or if your partner has a low sperm count. If you keep trying for up to six times you do increase your chances of becoming pregnant.

The timing of the insemination is crucial, so your partner must be able to produce a sperm sample by ejaculating into a cup on demand at the clinic.
It may be uncomfortable if it proves difficult to insert the catheter. And the procedure may cause cramps similar to period pains.
With stimulated cycles there is a very small risk of developing ovarian hyperstimulation syndrome (OHSS). This serious condition happens when your ovaries respond too well to the fertility drugs that cause you to ovulate. The ovaries rapidly swell up to several times their normal size and can leak fluid into your tummy, making you gain weight and feel full and bloated.
It’s vital that you seek medical help if you think you are experiencing OHSS. You may need to stay in hospital while your ovaries settle down, and your doctor will probably advise cancelling your IUI treatment for this cycle. That’s because the risks of conceiving a multiple pregnancy will be too great.