Hoppus revealed recently that he has been battling cancer and is now due to take a test to check his life expectancy.
The 49-year-old said that he had been taking chemotherapy for three months, and would continue to receive treatment for months to come.
He told his fans on Twitter that the test he'll take this week 'may very well determine if I live or die'.
Hoppus tweeted: "Apologies if I'm oversharing but it's so surreal to think that this week I'll take a test that may very well determine if I live or die.
"Thanks to everyone for the positive thoughts and encouragement. I read all your replies and it means the world to me.
He continued: "Apologies if I'm oversharing but it's so surreal to think that this week I'll take a test that may very well determine if I live or die.
"Thanks to everyone for the positive thoughts and encouragement. I read all your replies and it means the world to me. Thank you."
Fans have been quick to rally around the pop-punk musician, with one tweeting to say: "Sending prayers brother I love u very very much."
Hoppus has been keeping his fans updated on his condition, as well as providing updates on a garden that he's started creating since his diagnosis.
He said: "I put together a little cancer garden in the yard with mutated varieties because I feel connected to them through my own cells' mutation.
"I sit here in the morning with them, drinking my coffee, and we're like 'well this is weird...'."
Obviously, there have been problems. Chemotherapy is pretty tough, after all.
Hoppus said: "Everything about chemo sucks except the part where it hopefully saves me life."
Talking to fans on Twitch after an appointment for treatment, he said: "How am I feeling today? I feel much better than yesterday.
"Yesterday was hellish for me and I woke up today feeling better. I went for a walk, and I had a decent breakfast, and I haven't felt like I was going to throw up today, so we'll take it as a win.
"On good days, I go do stuff. I went on a walk outside today and it was the first time I'd left my house in like... five days pretty much.
"But this round of chemo I wasn't totally stuck on the couch, miserable. I've actually watched movies and walked around and cleaned the house and hung out with my dogs.
"I didn't just feel like a poisoned electrified zombie leaning up against an electric fence like I did the rest, the past couple of rounds."
Here's hoping that Mark responds well to the treatment and makes a full recovery.
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