Nigeria is facing its worst economic crisis in decades, with skyrocketing inflation, a national currency in free-fall and millions of people struggling to buy food. Only two years ago Africa’s biggest economy, Nigeria is projected to drop to fourth place this year.

The pain is widespread. Unions strike to protest salaries of around $20 a month. People die in stampedes, desperate for free sacks of rice. Hospitals are overrun with women wracked by spasms from calcium deficiencies.

The crisis is largely believed to be rooted in two major changes implemented by a president elected 15 months ago: the partial removal of fuel subsidies and the floating of the currency, which together have caused major price rises.

A nation of entrepreneurs, Nigeria’s more than 200 million citizens are skilled at managing in tough circumstances, without the services states usually provide. They generate their own electricity and source their own water. They take up arms and defend their communities when the armed forces cannot. They negotiate with kidnappers when family members are abducted.

But right now, their resourcefulness is being stretched to the limit.

No Money for Milk

On a recent morning in a corner of the biggest emergency room in northern Nigeria, three women were convulsing in painful spasms, unable to speak. Each year, the E.R. at Murtala Muhammed Specialist Hospital in Kano, Nigeria’s second-largest city, received one or two cases of hypocalcemia caused by malnutrition, said Salisu Garba, a kindly health worker who hurried from bed to bed, ward to ward.

Now, with many unable to afford food, the hospital sees multiple cases every day.

Mr. Garba was sizing up the women’s husbands. Which source of nutrition he recommended depended on what he thought they could afford. Baobab leaves or tiger nuts for the poor; boiled-up bones for the slightly better off. He laughed at the suggestion that anyone could afford milk.

More than 87 million people in Nigeria, Africa’s most populous country, live below the poverty line — the world’s second-largest poor population after India, a country seven times its size. And punishing inflation means poverty rates are expected to rise still further this year and next, according to the World Bank.

Last week, unions shut down hospitals, courts, schools, airports and even the country’s Parliament, striking in an attempt to force the government to increase the monthly salary of $20 it pays its lowest workers.

But over 92 percent of working-age Nigerians are in the informal sector, where there are no wages, and no unions to fight for them.

For the Afolabi family in Ibadan, in southwestern Nigeria, the descent into poverty started in January with the loss of an electric tuk-tuk taxi.

Forced to sell the taxi to pay his wife’s hospital bills after the difficult birth of their second child, Babatunde Afolabi turned to occasional construction work. It paid badly, but the family managed.

“We had no thoughts about starvation,” he said.

But then, he said, cassava — the cheapest staple in many parts of Nigeria — tripled in price.

All they can afford now, he said, is a few biscuits, a little bread, and for their 6-year-old, 20 peanuts a day.

A Country Built on Gas

Nigeria is a country heavily dependent on imported petroleum products, despite being a major oil producer. After years of underinvestment and mismanagement, its state refineries produce hardly any gasoline.

For decades, the national soundtrack has been the hum of small generators, fired up during daily power outages. Petroleum products move goods and people around the country.

Until recently, the government subsidized that petroleum, to the tune of billions of dollars a year.

Many Nigerians said the subsidy was the only useful contribution from a neglectful and predatory government. Successive presidents have pledged to remove the subsidy, which drains a hefty chunk of government revenue — and later backtracked fearing mass unrest.

Bola Tinubu, who was elected Nigeria’s president last year, initially followed through.

“It was a necessary action for my country not to go bankrupt,” Mr. Tinubu said in April, at a meeting of the World Economic Forum in Saudi Arabia.

Instead, many Nigerians are going bankrupt — or working multiple jobs to stay afloat.

Mr. Garba, the hospital worker, used to be solidly middle class, even though 17 family members, including 12 children, depended on him.

After shifts at the hospital, where he is setting up the first statewide ambulance service in addition to working in the emergency room, for which he is paid $150 a month, he heads to the Red Cross. There he occasionally receives a $3.30 volunteer stipend for helping tackle a severe diphtheria outbreak.

At night, he works at the pharmacy that he and a colleague set up. But few people have money for medicine anymore. He sells about $7 worth of medication per day.

Last year, Mr. Garba sold his car when the gas subsidies were removed, and now takes a tuk-tuk to work. Unable to power the generator, he reads medicine labels at the pharmacy by the light of a small solar lantern. He can only afford to buy rice and cassava in small quantities.

Life under the previous government was very expensive, he said, but nothing like today.

“It’s very, very bad,” he said.

It’s gotten so dire that there have been several deadly stampedes for free or discounted rice distributed by the government — including one in March at a university in the central state of Nasarawa where seven students were killed.