A young mother died from liver failure after she took "a few extra tablets" of paracetamol to ease the pain of a minor operation.
Desiree Phillips, 20, was prescribed antibiotics and paracetamol by doctors, following surgery to remove a number of benign lumps on her breasts.
Her grandfather Des Phillips said he believed she was taking just "a few extra tablets" a day to cope with the discomfort.
The single mother, from Llanelli, South Wales, was admitted to hospital nine days after the operation in excruciating pain and diagnosed with liver failure.
She underwent a liver transplant but her body rejected the new organ. She died at Birmingham Queen Elizabeth Hospital a week later, on 26 August.
Mr Phillips, said: "She must have been taking a few extra tablets than the recommended eight a day. She seemed fine to us, then out of the blue her boyfriend found her stretched out on the sofa.
"When we heard she was at hospital we never expected she might die. People don’t realise that an extra two over a period of time can harm your liver if you keep taking that over two to three weeks."
He added: "We have lost part of our heart, losing her like this."
Miss Phillips' family are urging action to be taken to prevent similar tragedies happening in the future.
Mr Phillips said: “If a painkiller is that dangerous, it should be prescribed. Cigarettes have a label saying 'smoking kills' but paracetamol packets don’t look dangerous.”
The young mother’s funeral was held at Llanelli Crematorium yesterday. Her one-year-old son Jayden is being cared for by his father, Simon Dewi-Jones.
Miss Phillips' mother, Ayshea, 38, said: "Jayden doesn’t deserve to be growing up without a mum because of this."
Recent research, published in the British Journal of Clinical Pharmacology, revealed that people who regularly take slightly too much paracetamol over a period of time to relieve pain could be at a higher risk of dying than those who take a one-off overdose of the drug.
Dr Kenneth Simpson, who worked with the University of Edinburgh and the Scottish Liver Transplantation Unit, said: "They haven't taken the sort of single-moment, one-off massive overdoses taken by people who try to commit suicide, but over time the damage builds up, and the effect can be fatal."