Doctors across Gaza described operating on patients without anesthesia, turning away people with chronic conditions, and treating rotting wounds with limited medical supplies.
"We have patients screaming for hours because of a shortage of painkillers," one told the BBC.
The World Health Organization (WHO) has described the state of healthcare in Gaza as "beyond words".
It said 23 hospitals in Gaza were not functioning at all as of Sunday - 12 were partially functioning and one was minimally functioning.
The health agency said the airstrikes and lack of supplies had "destroyed an already low-resource system".
The Israel Defense Forces (IDF) said that Hamas "systematically uses hospitals and medical centers for their terrorist activities".
In a statement to the BBC, it said the IDF "did not 'attack' the hospitals, but entered specific areas... [] to neutralize Hamas infrastructure and equipment and to capture Hamas terrorists, working with extreme caution".
It said it was allowing humanitarian aid, including medical supplies, into Gaza.
Aid agencies, including the WHO, say there have been "repeated access restrictions and denials".
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Hospitals are expanding
Health workers say many hospitals in Gaza are overcrowded and have limited equipment. There are reports that some hospitals in southern Gaza are operating at over 300% of their bed capacity.
According to the WHO, four field hospitals with 305 beds have been established in Gaza.
On Sunday, it said the Nasser hospital in southern Gaza was the latest facility to become defunct following an Israeli forces operation.
The IDF said on Sunday night that it had found weapons as well as drugs with the hostages' names and photos at the hospital and had detained "hundreds of terrorists" hiding there. "Hamas has put Gaza's most vulnerable citizens in grave danger by using hospitals for terror," it previously told the BBC.
Staff at nearby hospitals say Nasser's operation has put extra stress on them.
Youssef al-Akkad, director of the Gaza European Hospital in the southern city of Khan Younis, described the current situation there as "the worst we've seen since the beginning of the war".
"This situation was dire before, so how do you feel after you've got thousands more who have been displaced and are now staying in hallways and public areas?"
He said the hospital did not have enough beds to treat patients, so staff were laying sheets on metal frames and wood and "putting many patients on the floor without getting anything".
Other doctors across the Gaza Strip described similar situations. "Even if someone has cardiac arrest or cardiac problems, we put them on the floor and start working on them," said Dr. Marwan Al-Hams, director of Rafah Shaheed Mohammad Yusuf Al-Najjar Hospital.
A political committee of Hamas appoints the director of Gaza's public hospital. In some cases, these managers were in place before Hamas took control of the Strip.
Medicines and supplies
Doctors say they are struggling to work with limited medical supplies. "We can't find a single drop of oxygen," one told the BBC.
"We are running out of anaesthetics, supplies for the ICU, antibiotics and finally painkillers," said Dr Al-Akkad. "There are many people who are severely burned... we don't have any suitable painkillers for them."
A doctor confirmed that the operation was being performed without anesthesia.
A WHO team said they recently met a seven-year-old girl in a European Gaza hospital with 75% burns, but were unable to get pain relief because of low supplies.
Dr. Mohammad Salha, acting director of Al-Awda Hospital in northern Gaza, said people were taken there for treatment on donkeys and horses.
"The disaster is when patients have wounds that are decomposing, because the wounds are open for more than two or three weeks," he said.
He said that due to power shortage, the doctors there performed the surgery by the light of head torch.
Workers are separated from families
The WHO says there are about 20,000 health workers in Gaza, but most are not working "as they struggle to provide for their families".
Dr Al-Akkad said the number of staff and volunteers at his hospital had increased, partly due to displaced people coming from other areas to help. But he said that was not enough to handle the volume of patients and the type of injuries they suffered.
After the bombing, he said the wounded arrived at the hospital "like a kofta" - a dish of ground meat.
"The same person comes in with brain injuries, broken ribs, broken limbs and sometimes the loss of an eye... Every injury you can imagine, you can see in our hospital."
A patient may need five or more specialist doctors to deal with the extent of the injury, he said.
Some doctors who continue to work are estranged from their families.
"My family has been away from me for more than three months and I am eager to embrace them," said Dr Salha from northern Gaza, whose family has sought safety in the south.
"My consolation is that I am here serving children, women and the elderly to receive healthcare and save their lives."
No room for chronic patients
Doctors told the BBC that people with chronic conditions in Gaza "have paid a heavy price".
"Frankly we have no beds for them or any possibility to follow up with them," said Dr Al-Akkad.
"Someone who was on dialysis four times a week, now he's doing it once a week. If this guy was doing 16 hours a week, now it's one hour."
Some women are giving birth in tents without medical assistance, while hospitals providing midwifery services say they have limited capacity.
"A person dies in one section and a new life is born in another section. Babies are born and there is no milk for them. The hospital provides one box of milk for each baby," said Dr Salha.
People are coming to hospitals with diseases spread in crowded and unsanitary conditions.
"The disease is there and we can't find a cure," said Abu Khalil, 54, who is displaced in Rafah, southern Gaza.
"We have to go out at dawn and stand in a line and you'll probably get 100 people in front of you. You go back empty-handed."
