The candidates also discussed the opioid epidemic and the shortage of substance abuse treatment beds — in New Hampshire and nationwide.

Here are some highlights and related fact checks:

Klobuchar and Buttigieg, the former mayor of South Bend, Ind., sparred over his record of support for Medicare for All, the single-payer health care bill Sanders backs. Klobuchar noted that Buttigieg previously tweeted in favor of the bill and has since changed his position. Buttigieg said he has been consistent on supporting an approach that would bring health care to all Americans.

Klobuchar's point — that Buttigieg has at least expressed support for the specific bill, and no longer does — is supported by evidence.

The tweet was posted on Feb. 18, 2018. Buttigieg wrote, "I, Pete Buttigieg, politician, do henceforth and forthwith declare, most affirmatively and indubitably, unto the ages, that I do favor Medicare for All, as I do favor any measure that would help get all Americans covered."

Since then, Buttigieg has narrowed his stance — backing "Medicare for all who want it," a plan he argues would also achieve universal coverage, by letting people opt into a public health plan, and offering more generous subsidies for those who purchase private insurance. (Proponents of single-payer are skeptical it would succeed.)

To be fair, even Buttigieg's 2018 statement includes an important qualifier — he's not tied to the plan. He favors Medicare for All, he says, as he does "any measure that would help get all Americans covered." If you agree that his current plan would also achieve universal health care, there's an argument that he has been consistent.

—Shefali Luthra

This is in reference to Medicare for All. We contacted Biden's campaign, who directed us to the 2018 federal budget — $4.1 trillion — compared to the estimated $32 trillion price tag of Sanders' single-payer proposal. But there's a problem: That latter number is an estimate of the cost for 10 years. So putting one year of the budget against a decade of health spending is comparing apples and oranges.

And converting one year's budget to a decade-long forecast is an economically complex proposition — it's not so simple as just multiplying by 10.

We also ran this claim by an independent expert, who crunched the $32 trillion estimate. Linda Blumberg, an institute fellow at the Urban Institute, told us Biden's comparison is "an exaggeration" and "overstatement."

Certainly, she said, Medicare for All would be "a bigger increase to the federal budget than we've ever experienced" — more than a 70 percent increase, compared to the CBO's 10-year budget estimate.

"This is an enormous increase, but it wouldn't double" the budget, she said.

—Shefali Luthra

This is a favorite talking point from Sanders. We double-checked the math during the last debate. It holds up — and is probably an underestimate.

The figure is derived by adding the "net revenues" as reported by the companies for 10 pharmaceutical companies and 10 companies that work in health insurance. Multiple independent economists reviewed the methodology with, and affirmed that it's sound. In fact, the total "net revenue" — or profit — is actually around $101 billion.

The talking point doesn't include health care's biggest earners, though: hospitals and health systems. When you factor them in, experts previously told us, the level of profit in our system will grow significantly larger.

—Shefali Luthra

The way Sanders uses this number is problematic and oversimplifies the research. When we previously fact-checked this claim, we rated it Half True.

It appears that the number comes from Physicians for a National Health Program, which cited the Oregon Health Insurance Experiment, a study that assigned by lottery some participants to Medicaid and the others remained without insurance. A year into the experiment, researchers found that the death rate differed by 0.13 percentage points between those who were on Medicaid and those who were not — though this difference was not statistically significant. If you extrapolate this number to the number of Americans who are uninsured — about 27 million — then you do get close to a figure of about 30,000 people.

However, experts said that since the difference was not statistically significant it shouldn't be extrapolated so broadly, and it's possible that Sanders' number is too high. Other research does show that there is a connection between being uninsured and higher likelihood of mortality. Thousands of Americans die waiting for health care every year, but this number relies on imprecise math.

—Victoria Knight

This is true. If anything, it falls a little short.

The data comes from an estimate by the  Commonwealth Fund, a health care research and advocacy group. Researchers found that in 2018, 37 million non-elderly Americans — about 1 in 5 people — skipped a prescription because they couldn't afford it. Some of those people had coverage. Others were "underinsured." That means they had insurance, but it wasn't enough to safeguard them from large medical bills.

Other data suggests it's potentially even worse. A November poll from West Health and Gallup estimated that 58 million Americans experienced what they called "medication insecurity" in the past 12 months.

—Shefali Luthra

On the campaign trail, Warren has often mentioned that she would use the power of the executive office to reduce prescription drug prices for drugs such as HIV medication and EpiPens. We checked it, and it is true that the president has these executive powers.

Warren has in her "Medicare for All" transition plan a pledge that she would use two legal mechanisms to achieve this goal — "compulsory licensing" and march-in rights. Compulsory licensing means the government will take over a patent if a drug's prices are too high and create competition. There is precedent for this approach, it was done in the 1960s for cheap generic drugs and in 2001 for Ciprofloxacin during the anthrax scare. Experts said this likely couldn't be applied to all drugs but could work for insulin and EpiPens.

March-in rights are when the government "marches in" during a public health crisis because a drug isn't available. But, it only works for drugs in which the government holds all of the patents, such as Truvada, the HIV prevention drug. However, this mechanism has never been employed and it's unclear whether high prescription drug prices would qualify as a public health concern. Officials at the National Institutes of Health would also have to approve this measure, and it would face significant backlash from the pharmaceutical industry.

Warren is right that the laws are in place for her to reduce prescription drug prices without the power of Congress, but it's likely it would be difficult.

—Victoria Knight

Kaiser Health News is a nonprofit news service covering health issues. It is an editorially independent program of the Kaiser Family Foundation, which is not affiliated with Kaiser Permanente.

Read more: 

• House Democrat offers state-based Medicare for All bill
• Middle class the winners in Warren's Medicare for All plan
• 9 ways to finance Medicare for All, none of which look that great