The Scientist: Lauren F. Streicher, M.D., Clinical Associate Professor of Obstetrics and Gynecology at Northwestern University’s Feinberg School of Medicine, and author of Sex Rx: Hormones, Health, and Your Best Self Ever.

The Answer: There isn’t any hormonal reason some women feel totally drained during their period. It’s totally normal to feel mood swings or crave sweets or salt, but nothing about menstruation itself should be making you feel tired. Instead, a few of your habits, which are a reaction to how crummy you feel when you’re menstruating, could be contributing to your low energy levels.

Some women have trouble getting a good night’s sleep during that time of the month. Cramps and a heavy flow can both interrupt a smooth night of slumber, whether you’re waking up in pain, going to the bathroom to change your tampon, or getting up to pop some pain meds. Also, many women avoid exercise when they have their period. Sitting around and not exercising tends to make you feel more lazy and lethargic at any time of the month.

On top of all this, reaching for a heaping bowl of mac ‘n cheese isn’t the best way to sustain your energy. Making poor food choices, which many of us tend to do when we’re craving a little extra comfort, can just make you feel even more sluggish. (Here are some tips on what to eat during your period instead!)

The only real medical reason you could be unusually tired during your period is if you have anemia, which is an iron deficiency. For some women who are anemic and have a very heavy period, the first day can be a doozy.  However, this group is in the minority. If you know you’re treating your body right and are still walking around like a zombie during that time of the month, see your doctor to find out what’s up. A simple blood test can reveal if you’re anemic and it’s very easy to treat with iron pills or the addition of more iron-rich foods to your diet.

Bottom line: Figure out what’s draining your energy and fix it. You should be able to have your period without feeling exhausted.

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