Many Selenators grew concerned after the singer did an Instagram Live chat with Timothee Chalamet on Oct. 24 ... and viewers noticed a tube coming out of her arm.

As you know, Selena's dealt with major medical issues over the past 5 years -- including a lupus diagnosis and a kidney transplant -- but sources close to her tell us the IV was simply a vitamin drip.

We're told Gomez gets the IV drips regularly and they have nothing to do with her lupus or other health issues. As for why she chose to have it administered while she was live streaming ... our sources say it was just a timing thing, and Selena didn't care to hide it.

It's not like she's the only celeb known for drippin' ... Justin Bieber's got no qualms about it either.

More importantly, we're told Selena is fine and healthy, and has been staying very busy during the pandemic. Along with focusing on her career, she's also been working hard to encourage folks to vote in the election and advocating with other powerful women ... including Kamala Harris, Michelle Obama and Stacey Abrams.