Here's Why You Might Feel Weaker During Your Period

If you feel really tired and even physically weaker when you’re on your period, it’s not just all in your head.

Menstrual symptoms like cramps, bloating, mood changes, and headaches, aren’t the only things that can make you feel worn out—there are actually a few reasons why your period can be exhausting for your body and mind.

Here’s what experts say about why your energy levels tank during your period and what you can do to feel better.

Period Blood Loss Can Make You Tired

G Thomas Ruiz, MD, OB/GYN Lead at MemorialCare Orange Coast Medical Center in Fountain Valley, California, told Verywell that how tired or weak you feel on your period partly depends on how much blood you lose while you’re menstruating.

According to Ruiz, people who experience more than 80 milliliters of blood loss per month or heavy blood flow can become anemic. A person with anemia does not have enough healthy red blood cells to carry oxygen to their body’s tissues and organs. As a result, iron levels in the blood get lower, and this can cause symptoms of tiredness or weakness.

Becoming anemic during a menstrual cycle is not a long-term medical concern, but Cristin Hackel, MSN, ARNP, Medical Director, Nurx GYN Services, told Verywell that it can make a person feel more “fatigued and unable to do what they normally can do in a workout” or during other activities.

However, Hackel noted that a person’s iron levels typically return to normal within a few days after bleeding stops.

You May Not Sleep Well During Your Period

Some people notice their sleep is negatively affected by their menstrual cycle. In addition to making you feel lethargic, a lack of sleep can also affect how much energy you have for physical activity, such as biking, running, or lifting weights. 

Jennifer Wu, MD, OB/GYN at Lenox Hill Hospital in New York, told Verywell that a lot of her patients cite cramps and discomfort as the reasons they can't sleep.

Beyond a heavy blood flow and poor sleep, Ruiz added that stress, changes in eating habits, frequent urination, and other medical conditions like uterine fibroids can cause physical weakness and exhaustion during your period, too.

Tired On Your Period? Get Moving!

When you’re on your period, exercise might be the last thing you feel like doing, but experts say that a workout can help ease PMS symptoms.

According to Ruiz, one of the major advantages of working out during your cycle is that it can help with cramps and pain. People who work out frequently or intensely will circulate more endorphins throughout their workout, which function as a sort of pain killer.

Ruiz added that moving your body can also help boost your mood by releasing dopamine—a chemical released in the brain that makes you feel good. For example, dopamine is responsible for “runner’s high.”

Regular exercise can also help you maintain a body weight that’s right for you, which is important for regulating menstrual flow.

“Athletes often have very light flows because of their body fat,” Wu said. “Patients that have a lower body fat percentage do tend to have lighter menses.”

What Type of Exercise Is Best During Your Period?

It’s OK to continue your regular exercise routine during your period.

“Finding things that you want to do and enjoy will keep you working out and doing that exercise,” said Ruiz. “There’s not really an exercise that you can point to that’s better than the other; it’s just about finding the one you like.”

How to Make Working Out During Your Period Better

If you plan to exercise or just want to feel more at ease and comfortable during your period, Ruiz recommends choosing a menstrual product that suits your needs.

Consider swapping out pads for period underwear, tampons, or menstrual cups to allow for easier movement.

Wu added that people can consider taking a pain reliever like ibuprofen to help with painful cramps or other symptoms such as a headache.

People who have medium or heavy flows may want to talk with their healthcare provider about the use of hormonal contraception like birth control pills or hormonal IUDs.

“These options can give you a much lighter, regular and less painful flow, improve the quality of your periods, and improve your workouts during that time,” Wu said.

If you find that period-related symptoms, including tiredness or weakness, interfere with your day-to-day life, Wu recommends talking to your provider.

“Your period should not interfere with your daily life,” said Wu. “We need to do something about it if your flow is so heavy that you can’t exercise on certain days or can’t really go anywhere because you need to be close to the toilet. When your period is altering your life that much, then you should talk to your doctor about possible solutions.”