If you’re starting birth control for the first time, or switching types, you have a ton of different options. While it’s great to have so many choices, it can make the decision a tough one. There are many reasons both medically and personally, that lead individuals to pick one over another. Some of the most common forms of birth control are the pill, shot, ring, and patch. They each require different methods of use, and they have varying effectiveness.

As you’re making your decision, it’s likely that you’ll have questions. For example, what are your options? How do you take them? How effective are they? And the biggie: how long will you need backup contraception before your new birth control kicks in?

Below is the rundown on common birth control options, including when your birth control is the most effective.

The Pill

Birth control pills are one of the most commonly known forms of contraception. Patients take them by mouth daily to prevent pregnancy. If taken each day at precisely the same time of day, the pill is 99% effective. However, with the margin of human error it’s more like 91% effective.

If you’re inconsistent with the pill and miss days, it lowers the effectiveness of it. Nine in 100 women have an unplanned pregnancy each year even though they are on the pill. This is largely due to not taking it consistently.

The pill takes seven days to be effective, so be sure to use another form of birth control until then. If you miss one pill, take it as soon as you remember. Then, the next step varies. Depending on the pill you’re on, you may need to use backup contraception again for at least a week. Check in with your doctor if you’re uncertain what to do or if you’ve missed more than one pill.

Here’s how the pill works: different hormones in birth control pills work to protect against pregnancy. These are estrogen and progestin. Some types of pills contain both, and others contain only progestin. Your doctor will help you decide what’s best based on your medical history. For example, you might be prescribed progestin only pills if you have risk factors for stroke and blood clots.

Depending on the hormone level and type of pill you take, pregnancy is prevented in different ways. Some stop or reduce ovulation. Others keep sperm away from the egg by thickening cervical mucus. Some thin the lining of your uterus, making it harder for an egg to attach. No matter which pill, you’ll need to take it every day.

The Shot

For those who don’t want to remember to take a pill every day, the shot can be a good option. It can also lessen or stop your period and reduce cramps. You get the birth control shot, Depo-Provera, every three months.

Taking the shot within seven days of when your period starts will protect you that day. If you take the shot during any other time, you’ll have to wait seven days for it to be effective. Use alternative methods of birth control, such as a condom, until then.

The shot contains the hormone progestin, and prevents ovulation, and also thickens cervical mucus. It’s 94% effective, and it can be given to you by your healthcare provider. You can also get it delivered to your home to do yourself.

Either way, it’s important to remember to get it every 12-13 weeks for it to be effective. Make sure to mark the day in your calendar so that you don’t forget.

If you’re late taking the shot, you’ll have to use backup contraception again. If you’re two weeks late getting it, your healthcare provider might even have you take a pregnancy test.

The Ring

The ring is also called the vaginal ring. If used correctly, it’s considered 91% effective.

Its name explains the design. It’s a ring that you place inside your vagina that releases the hormones into your vaginal lining to prevent pregnancy. The ring contains both estrogen and progestin, so it prevents ovulation and thickens cervical mucus as well.

There are two kinds of vaginal rings: NuvaRing and ANNOVERA. With NuvaRing, you insert a new ring into your vagina once a month. With ANNOVERA, the ring is good for a year.

The ANNOVERA ring does take a bit of extra maintenance, though. You leave it inserted for three weeks and then take it out for seven days, all on a monthly cycle. You’ll also need to clean it properly.

Insert the ring within the first five days of your period, and it protects you right away. Like the pill and shot, if you start other times during the month, it takes seven days to work. If you engage in sexual activity during this time, use other methods of contraception to be safe.

The Patch

The patch is also considered 91% effective in pregnancy prevention when used properly. This option however, requires weekly replacements. It’s recommended that you wear the patch on specific parts of your body, depending on which brand you are prescribed. For example, many patch prescriptions suggest placing it on your bum or belly. One patch can even go on your upper arm.

The way the patch works is similar to the shot in that it prevents ovulation and thickens cervical mucus. In this case, the hormones estrogen and progestin enter your body through the skin.

Forgetting to change your patch or refill your prescription could lead to an unplanned pregnancy. Keep track of the date you need to replace it. It’s also important to keep your other patches at room temperature.

Starting the patch when your period starts, or within five days of it starting, protects you right away. If you start the prescription at other times of the month, you’ll need to wait seven days until you’re protected. For that first week, be sure to practice safe sex with other techniques.

Getting new or different birth control can be a freeing experience. It might be a huge weight off your shoulders to feel protected against pregnancy. However, remember that none of these options prevent sexually transmitted infections.

Condoms and internal condoms, on the other hand, do help prevent STDs and pregnancy. Using condoms with your birth control can help ensure that you stay safe and that you won’t get pregnant. Another bonus is that condoms work instantly to protect you.

When you’re making a decision about which birth control to start, assess your medical history with your doctor. Some prescription medications can actually make your birth control less effective. So be honest with your doctor, and when you’re prescribed a new medication, ask how it’ll impact your birth control.

No matter which birth control method you end up choosing, knowledge and consistency are key. Make sure that you understand how to use it and when it becomes effective. Many unexpected pregnancies occur simply because people don’t carefully follow all of the directions.