Camilla Luddington thought she was just experiencing the normal effects of aging until she was recently diagnosed with an autoimmune disease that explained the symptoms she’d been experiencing.

On the latest episode of her Call It What It Is podcast, which she co-hosts with her Grey’s Anatomy costar Jessica Capshaw, Luddington opened up about her health, revealing she underwent bloodwork earlier this year, which came back with surprising results.

“About two-and-a-half months ago — now still very recent — I had blood work,” Luddington said. “It came back, and my doctor was like, ‘Everything looks great except this one little thing. And I remember hearing the words autoimmune disease and thinking, ‘What the f***?’ And then being told that I had something called Hashimoto’s hypothyroidism and that it was very common.”

According to the Mayo Clinic, “Hashimoto’s disease is an autoimmune disorder affecting the thyroid gland”, caused by “the immune system attacking healthy tissues,” and “it’s most common among middle-aged women.”

Luddington, who has played Dr. Jo Wilson on the ABC medical drama since 2012, admitted she was “a little freaked out” when she first received the news. However, eventually, she said she was “relieved.”

“I felt like I had the answer for something that I’ve been knowing is going on. And I have health anxiety, so there was a part of me that was like, ‘Am I gaslighting myself?’” she continued.

The symptoms of the disease can include feeling fatigued and sluggishness (or “slothy,” as Luddington called it), increased sensitivity to cold, dry skin, muscle weakness, hair loss, depression, and more.

“What it can make you feel is tired and cold, which is really funny because Matt would make fun of me, because I’d have like 40 blankets on me at night,” Luddington shared, referencing her husband, 13 Reasons Why actor Matthew Allan. “It can make you foggy, depressed, you can have dry skin, your hair can thin.”

Luddington, who turned 41 in December, wondered at first if she was experiencing these things due to getting older. “I thought, ‘I have two kids, I’m in my 40s. This is what ‘the 40s’ is: You know, I have jobs to do, maybe I’m perimenopause,’” she said.

The actress added, “It got to the point where, by 11 a.m., I felt like I had to chug Benadryl, and I needed to nap. It didn’t matter how much sleep I’d gotten the night before. There was no pushing through the day.”

Now, though, Luddington is taking medication to help combat the symptoms, noting she will return to her doctor every six weeks to monitor the progress.