Chronic fatigue syndrome is not simply being “tired.” It’s a debilitating chronic illness with symptoms that affect sleep, concentration, pain and energy. More than one million Americans have the condition, according to the Centers for Disease Control and Prevention.

Because chronic fatigue symptoms are typically invisible and thus misunderstood — or even dismissed — by people who don’t have the condition, The Mighty asked our readers as well as the ProHealth community to describe what chronic fatigue really feels like.

Here’s what they told us:

1. “The best way to describe chronic fatigue is looking through a foggy glass every day. Nothing ever seems real; it always seems dreamlike.” — Kathrine Elise

2. “It feels like I have concrete in my veins. My legs are heavy and my arms do not want to move. I ache. Trying to fight off sleep is fruitless sometimes; best to give in before I pass out.” — Judith Brain

3. “Imagine plugging in a dead cell phone over night. When you awake, you expect it to be at 100 percent. But when you wake, it’s only at 9 percent and you have to try and function on that 9 percent. You’re never fully charged.” — Michelle Lewis

4. “Chronic fatigue feels like I’ve gotten hit by a truck. It doesn’t matter how much sleep you get. My body feels heavy, and it’s a struggle to have the energy to do anything.” — Megan Rosvanis

5. “It feels as though days have no beginning and no end. Very much like not being able to participate fully in your own life due to the overwhelming weight of the perpetual, debilitating exhaustion.” — Kaitlyn Michaud

6. “I often feel like a limp dish rag. It’s hard to put one foot in front of the other and to sit up for long.” — Sharon Anderson

7. “It feels as if you are walking through mud. The mud is up to your waist and you can hardly move your legs. Your eyes feel like they weigh 100 pounds and you can hardly keep them open.” — Hannah Waldron

8. “Fatigue is an invisible full length cloak, weighted all around so your reality is this heavy, filmy, dense shroud. Wearing it constantly saps your energy, but there is no clasp to remove it from your body. It makes movement slow, awkward and exhausting. The cloak of fatigue grows tolerable at times, but there is no shrugging off the weight completely.” — Erica Cai Fish

9. “It’s like swimming upstream every moment you’re awake and your brain is in a fog like when someone hasn’t slept for two to three days straight.” — Oriana Hill

10. “No amount of sleep I get will be enough. That feeling people have first thing in the morning after a bad sleep is what I have all day, every day.” — Calliope Krystal Pia Kilpeläinen

11. “A cross between the flu and being intoxicated 24/7.” — Twilight Maher

12. “It’s like when Superman gets to close to kryptonite. It feels like the energy is literally being sucked out of my body.” — Ashley Garcia

13. “It’s like a cross between a pin cushion and a tanker running over you 10 times forwards and backwards, plus a fluffy cloud inside your head not deflating until you move… then pop!” — Robyn Ager

14. “Imagine having to lean against your desk at work in order to sit up, and having to prop yourself up on your forearms at the sink so you can wash dishes, budgeting trips up and down stairs and having to rest after you shower.” — Eleanor Martino

15. “It feels as if you moved an entire house full of furniture up five flights of stairs by yourself.” — Denise Noble Hall

16. “Doing everything a ‘normal’ person does… in a vat of Jell-O.” — Emily Matejic Souders

17. “Like the sun never comes out, the Folger’s never brewed and like I live in a constant fog.” — Tiffany Irvin

18. “Walking for five minutes feels like running a marathon.” — Sarah Norfolk