Why is my girlfriend moody before her period?

In the days before a period many people sleep worse and run shorter on patience, so her clipped replies often say more about her week than about you. Skip the hunt for what you did wrong, stay close, and let her choose company or quiet.

What's actually going on

You ask about her day and get "Fine." You ask what she wants for tea and get a sigh. Last night she snapped at you for leaving the cupboard door open, which, fair enough, but it came out sharper than usual. Then she said "I'm fine. Just tired." and went to bed at half nine.

For many people the days before a period bring poorer sleep, less patience and a lower mood that doesn't seem to have a cause. Some feel it hard. Some barely notice. Cycles vary a lot between people, so any guess about where she is in hers stays a rough guess.

Two things can be true at once. Her mood can be lower for physical reasons, and her point about the cupboard can still be fair. Writing off everything she says as her period is dismissive, and she'll feel it.

Short answers aren't a verdict on you or on the relationship. Often she's tired and has less to give.

What not to say

Picture Wednesday evening. She's quiet through dinner, answers in single words, and goes to load the dishwasher without looking at you. You follow her into the kitchen and ask, "What did I do?"

To you it's the responsible question, because you want to put things right. To her it lands as a job: reassure you, go back over your week, or come up with a reason on the spot. She was already running low, and now she's standing by the dishwasher defending a mood she didn't choose. Adding "Is it that time of the month?" would have made it worse, because even when that guess is right it tells her that her feelings don't count. Leave that one out entirely, joking or not.

What to say instead

Make it clear you're staying, and let her set how much contact she wants:

"I'm not going anywhere. Want company or quiet?"

It's calm, it doesn't ask her to explain, and either answer is fine with you. On a night when she looks wiped out and you suspect she won't want to decide anything, try "Long week? I'll sort dinner." If she's said she wants quiet and you're both on the sofa anyway, "No need to talk. I'll be here." is enough.

If you did do something, she'll tell you, maybe later, maybe after a decent night's sleep. There's room for that conversation tomorrow.

What to do

Ask yourself what would make tonight a bit easier for her, and do that. Usually the answer is practical.

Cook something she likes, or order it. Switch the big light off and the small lamp on. Put a bowl of whatever snack she's been eating lately on the table. If she's heading to bed early, let her, and keep the noise down. If she's sleeping badly, don't be the one scrolling videos with the sound up at midnight.

Keep your own temper. If she's short with you, you don't have to match it, and you don't have to swallow everything either. "That came out a bit sharp" said calmly the next day is fair. Said in the middle of a tense evening, it usually starts a row.

Over a few months, notice the pattern, privately. If the tense days tend to bunch together, you can plan round them a little with fewer big social plans and a slow weekend, without announcing it or treating her like a weather forecast.

When it's more than normal

Notice whether the low patch lifts once her period starts, or whether it hangs on. A mood that drops so far she can't work or face people, a sense of hopelessness, or a change that's suddenly much worse than it used to be is worth her talking to a doctor about. Severe pain that stops her doing daily things, or bleeding far heavier than normal for her, belongs on the same list. Supporting her might mean helping her book the appointment, going with her if she wants, and taking her seriously when she says it's hard.