In many cases, volunteer groups have come to the rescue.
India's tally of coronavirus infections rose on Monday to just short of 20 million, propelled by a 12th straight day of more than 3,00,000 new cases, as scientists predicted the pandemic could peak in the next couple of days.
Total infections since the start of the pandemic have reached 19.93 million, swelled by 3,68,147 new cases over the past 24 hours, while the deaths rose by 3,417 to 2,18,959, health ministry data show. At least 3.4 million people are currently being treated.
But medical experts say actual numbers could be five to 10 times higher.
Hospitals have filled to capacity, supply of medical oxygen has run short and morgues and crematoriums have been swamped as the country grapples with the surge. Patients are dying on hospital beds, in ambulances and in carparks outside.
"Every time we have to struggle to get our quota of our oxygen cylinders," said BH Narayan Rao, a district official in Karnataka's Chamarajanagar, where 24 COVID-19 patients died, some from a suspected shortage of oxygen supplies.
"It's a day-to-day fight," added Mr Rao, as he described the hectic scramble for supplies.
In many cases, volunteer groups have come to the rescue.
Outside a temple New Delhi a group of Sikh volunteers is providing oxygen to patients lying on benches inside makeshift tents, hooked up to a giant cylinder. Every 20 minutes or so, a new patient comes in.
"No one should die because of a lack of oxygen. It's a small thing otherwise, but nowadays, it is the one thing every one needs," Gurpreet Singh Rummy, who runs the service, told Reuters. He called it an oxygen "langar".
Offering a glimmer of hope, the health ministry said positive cases relative to the number of tests fell on Monday for the first time since at least April 15.
Modelling by a team of government advisers shows coronavirus cases could peak by Wednesday this week, a few days earlier than a previous estimate, since the virus has spread faster than expected.
At least 11 states and regions have ordered curbs on movement to stem infections, but Prime Minister Narendra Modi's government is reluctant to announce a national lockdown, concerned about the economic impact.
"In my opinion, only a national stay at home order and declaring medical emergency will help to address the current healthcare needs," Bhramar Mukherjee, an epidemiologist with the University of Michigan, said on Twitter.
"The number of active cases is accumulating, not just the daily new cases. Even the reported numbers state there are around 3.5 million active cases."
CRISIS TESTS PM MODI
As medical facilities near breaking point, the government postponed an exam for doctors and nurses on Monday to allow some of those still in training to join the coronavirus battle alongside existing personnel, it said in a statement.
India is facing one of its biggest crisis since PM Modi took office in 2014. He has been criticised for not moving sooner to limit the spread and for letting millions of largely unmasked people attend religious festivals and crowded political rallies in five states during March and April.
In early March, a forum of government scientific advisers warned officials of a new and more contagious variant of the coronavirus taking hold, five of its members told Reuters.
Despite the warning, four of the scientists said the federal government did not seek to impose major curbs.
With the next general election due in 2024, it remains to be seen PM Modi's handling of the crisis might affect him or his party. His party was defeated on Sunday in West Bengal state poll, although it won in Assam.
Leaders of 13 opposition parties urged PM Modi in a letter on Sunday to immediately launch free national vaccination and to prioritise oxygen supply to hospitals and health centres.
Several states have postponed widening a vaccination drive for adults that was to start on Saturday due to a lack of vaccines.
Despite being the world's biggest producer of vaccines, India does not have enough for itself. Just 9% of a population of 1.35 billion has received a dose.
India has struggled to increase capacity beyond 80 million doses a month due to lack of raw materials and a fire at the Serum Institute, which makes the AstraZeneca vaccine.
Another manufacturer, Pfizer Inc, is in talks with the government for "expedited approval" of its vaccine, Chief Executive Albert Bourla said on LinkedIn, announcing a donation of medicines worth more than $70 million.
Last month, India said its drugs regulator would hand down a decision within three days on emergency-use applications for foreign vaccines, including that of Pfizer.
International aid has poured in, in response to the crisis.
Britain will send another 1,000 ventilators to India, the government said on Sunday. Boris Johnson and PM Modi are set to talk on Tuesday.
The Indian COVID-19 variant has now reached at least 17 countries including Britain, Iran and Switzerland, spurring several nations to close borders to travellers from India.