Medicare charges to patients for the first day of hospitalization will take a big jump on Jan. 1, rising from $400 to $492, according to a new payment schedule drafted by the Department of Health and Human Services.

That's the bad news. The good news is that the premium the patient pays for the doctor-insurance portion of the program will remain $15.50 per month because program outlays were lower than anticipated.

The payment schedule, to be published next week in the Federal Register, lays out various fees patients must pay in 1986.

Under the law, a Medicare patient is required to pay, either personally or through private insurance, a set fee for the first day of each hospital stay, with certain exceptions. Medicare then pays the entire charge for covered hospital services from the second through 60th days, and the patient pays a portion of the cost from the 61st to 90th days.

Fees and coinsurance also are required for nonhospital services. The amounts patients must pay generally rise each year to reflect increases in costs.

Here is the new schedule for 1986:

*For the first day of hospitalization the patient will be required to pay $492 instead of the current $400. The steep increase reflects the drop in the average length of hospital stays. The first day now is a larger proportion of the overall cost. This trend is not expected to continue at the same pace, so future increases in the required payment probably will be smaller.

*For the 61st through 90th days, the portion of the cost the patient must pay will rise from $100 to $123 per day. For any days that Medicare covers beyond that, the charge will rise from $200 to $246.

*For care in a skilled nursing facility, the charge to the patient for the 21st to 100th days will rise from $50 to $61.50 a day. Medicare pays the full cost for the first 20 days.