She was forced to cancel her Houston, Texas show due to an undisclosed illness.

And after apologising to fans for the last-minute cancellation of the latest stop in her Diamonds world tour, Rihanna was spotted leaving a doctor’s office in Beverly Hills on Tuesday.

Explaining the reasons behind the Houston concert not going ahead, Rihanna wrote on her Instagram account: ‘I was sick since San Diego!

I kept working because I thought two days off after the Vegas show would be enough time to recover and I f****ed up, those were two days off from hell and today is not different!

Just what the doctor ordered! Rihanna sucked on a lollipop as she left a doctor’s appointment in Beverly Hills on Tuesday after she was forced to cancel her Houston, Texas show due to an ‘undisclosed illness’

The two faces of Rihanna: The singer looked downcast as she left the doctor’s office, compared to her hard partying face on the tour bus en route to San Diego earlier this week

‘I’m sad and disappointed about it! I had all kinds of plans for Houston!’

The Houston show marks the third stop on the tour Rihanna has cancelled, following Boston and Baltimore.

Concert promoter Live Nation added that the cancellation was ‘as a result of illness’, although declined to reveal the exact nature of said illness.

They also told fans to keep hold of their tickets as the concert looks likely to be rescheduled.

Party bus: Rihanna, far right, appeared to be partying it up as she went to San Diego last weekend on a party bus to celebrate her best pal Melissa Forde’s birthday

Princess of china: Rihanna also posted another shot of herself wearing the turban and jewels while posing on the bus

But fans were left angry by the cancellation, with one writing to Rihanna on Twitter: ‘You not sick you out having fun. How dare you plan a tour then forget your responsibilities!! You need to also be focused on your career. I paid good money for these tickets n they were a surprise for my lil sis 18th bday n now we can’t even go!! (sic).’

And many fans have been speculating about the nature of Rihanna’s illness, as the singer has been seen partying in between her tour stops.

Rihanna has regularly posted shots of her antics on her Twitter and Instagram pages – most recently of which showed her and a group of friends celebrating the singer’s BFF Melissa Forde’s birthday on the bus en route to San Diego.

Undercover: The poorly star shielded her make-up face with a large black leather baseball cap featuring gold studded detailing and a pair of oversized shades

The image showed the singer sticking her tongue out while posing for the photograph.

And even when Rihanna has managed to perform, many fans have been left unimpressed by her lackluster appearance.

Commenting on the singer’s Las Vegas show, one fan even alleged she could have been on drugs, writing: ‘I went to her concert in las Vegas and she was clearly messed up. That was a day or two before her Houston concert was canceled.. She had to be coming down off the drugs or something. It was a hot mess.’

Another concurred: ‘Not a hot mess, just a mess. Really sad to watch. She forgot lyrics.. Could barely dance. It was sad.’

3rd time: This is the third show she has been forced to cancel after her Diamonds tour kicked off in March

Throat troubles: It is thought that Rihanna’s issue is again laryngitis as that was what led her to cancel the Boston stop of tour

Pictured leaving her doctor’s surgery on Tuesday, the You Da One star sucked on a lollipop as she left her appointment and headed to her awaiting chauffered car.

The poorly star shielded her make-up face with a large black leather baseball cap featuring gold studded detailing and a pair of oversized shades.

She had dressed down for her appointment in a pair of grey tracksuit pants teamed with a black hoodie and some Nike Air Jordan trainers.

Birthday time: Rihanna also looked healthy as she celebrated Melissa’s birthday by presenting her with a cake in her bed

A hug for my BFF: Rihanna wishes her best friend a happy birthday with a tender hug

Looking downcast, she shoved her hands in the pockets of her sweatshirt as she enjoyed her sweet treat.

But when some fans suggested Rihanna didn’t look that ill, another wrote in her defense on Twitter, saying: ‘How y’all know she ain’t sick she got shades and a hat on. y’all ain’t real fans. She ain’t gotta be all these name y’all calling her. I hope she really just didn’t skip out y’all like that. I just don’t think that’s her.’

The Diamonds World Tour is now set to resume on April 19 in Tampa, Florida.

Rihanna has already postponed two stops on her Diamonds World Tour since it started in early March.

Sick again: Rihanna was forced to cancel her stop in Houston on Monday evening due to illness

Not much help: There has been reports that her illness is self inflicted due to her love of drinking and partying

According to Hollywood Life, Rihanna has been struck down with laryngitis once again, which is what led her to cancel the stops of her tour.

A source told the website: ‘She feels bad, but what can she do? This cold and laryngitis … just ain’t the business, but she will bounce back. She just laying it down, trying to get better.’

Rihanna has a history of falling ill during tours, and has reportedly been told to curb her party-loving lifestyle if she wants to continue with her tour.

Shady business: The singer also posted this snap of herself with on and off boyfriend Chris Brown, captioning it ‘We shady!!!’

A source told The Sun newspaper: ‘Rihanna’s illness was so severe that doctors warned it could take months for her to fully recover – there were worries that she’d have to cancel her entire tour.

‘They’ve told her that she needs to make some serious lifestyle changes, or risk this happening again. This has given her a scare. But Rihanna knows it’s partly self-inflicted

‘She loves to smoke, drink and stay up late. Her body was bound to need a break at some point. She’s now on a mission to start looking after herself.’