The amount of federal loans that undergraduate students can borrow is capped each year, depending on the student’s year of college. The maximum is generally $5,500 for freshmen, $6,500 for sophomores and $7,500 for both juniors and seniors. The amount borrowed over all is limited to $31,000.

Students who need to borrow more may have their parents take out PLUS loans or turn to private loans made by banks and other lenders. Private loans, however, typically lack protections that come with federal loans, like the option to reduce your monthly payments to reflect your income.

When borrowers run into trouble, private lenders are not required to help them stay afloat, said Seth Frotman, executive director of the Student Borrower Protection Center, a nonprofit group that advocates reforms in the student loan industry.

“Private student loans should always be the very last option,” Mr. Frotman said.

Here are some questions and answers about student loans and student aid:

Can I get the new, lower interest rates on student loans I’ve already borrowed?

No. The rates apply to new loans borrowed from July 1 of this year to June 30, 2020; they don’t affect the rates on loans you already have. There’s no option to refinance federal student loans to take advantage of lower rates as you would with, say, a home mortgage. You can refinance federal loans only by paying them off with a new, lower-interest loan from a private lender — which means giving up some protections.

(Borrowers may “consolidate” federal student loans, which means combining them into a single loan so you have just one payment. The interest rate on the new loan is a weighted average of the old loans, though, so it doesn’t save you any money.)

Are there any fees charged for federal loans?

Yes. Fees are just over 1 percent of the amount borrowed for direct loans, and about 4.2 percent for PLUS Loans, for loans taken from October 2018 through Sept. 30, 2019.