with more, here's our health correspondent, amara sophia elahi.anjit senghera marwaha caught coronavirus in december last year and eventually ended up in hospital with seriously low oxygen levels. so basically, flip the lid, put yourfinger in... she had been monitoring her levels at home with a pulse oximeter, but the meter consistently told her she was in safe levels, even as she increasingly struggled to breathe. when i went into hospital, the first thing they said was, "you really did leave it too late". had you left it any longer, i would have been straight into icu. there is growing evidence that such monitors can overestimate oxygen levels in people with darker skin tones by 2%. that's led to nhs england and the body that regulates the use of medical devices, the mhra, issuing new advice. they say people shouldn't use the devices at home without speaking to a medical professional, and to monitor oxygen levels over time. low oxygen levels are a primary indicator of a serious covid infection, and those treating patients in hospital say they've