This is a good question because a lot of people who have vaginas are worried about whether they will bleed the first time they have penis-in-vagina sex. Many people don’t, but about 43% of people with vaginas do bleed the first time.   

You were right to assume that the bleeding came from your hymen. The hymen is a thin piece of tissue inside the vaginal opening. Most people with vaginas are born with a hymen. As you grow up, your hymen stretches, tears, or even breaks through day-to-day activities like riding a bicycle, playing sports, or using a tampon.  

You almost certainly have a hole (or holes) in your hymen by the time you have sex because that is how menstrual blood comes out. If that hole is smaller than a penis, though, penetration will stretch or tear your hymen even more. This can be uncomfortable and can cause bleeding.  

A quarter cup of blood sounds like a lot. Most people only see a few drops of blood after the first time they have intercourse. A quarter of a cup of fluid is actually more than most people lose during their period (which can last 7 days). Losing that much blood at one time after first sex would be unusual, but it is possible for the hymen to rip in places that causes a lot of bleeding.  

It’s also possible that you were about to get your period anyhow and the uterine contractions that can happen during sex and orgasm pushed the start button at an awkward moment.  

It’s also possible that you overestimated how much blood came out because it took you by surprise.   

As for bleeding the next time you went to the bathroom, that isn’t surprising. Some people bleed for a couple of days after their hymen is broken.  

You mentioned that you felt lightheaded a few minutes later. This could be a symptom of blood loss or illness, but it could also be an emotional reaction to the moment. The first time you try something new sexually can come with excitement and anxiety (which sometimes feel similar). Seeing blood—or more blood than you expected—afterwards may have increased that anxiety. People often feel lightheaded when they’re anxious. Of course, we’re just speculating. We don’t know details about the situation or what was going through your head.  

Vaginal bleeding can be a sign of other medical issues including some vaginal infections and some sexually transmitted infections. Given that this was your first time having penis-in-vagina sex, the chances that you already had a sexually transmitted infection (STI) are low, but not zero. STIs can be transmitted through other behavior like sharing sex toys that haven’t been properly washed.  

The likelihood that the bleeding after sex you experienced was anything to worry about seems small. That said, your physical and mental health are both very important. It’s a good idea to check with a health care provider if anything feels off or is worrying you.  

You should as know that using extra lubricant (lube) during penis-in-vagina sex can help reduce friction and prevent tiny tears in the vaginal walls. It can also make sex feel better. And, of course, it’s important to use condoms to prevent STIs and to choose a contraception method that will protect you from unintended pregnancy.    

—ASHA Staff