Is it better to work nights in a block?

It depends on whether the person keeps a night pattern on days off. ACEP's companion paper presents blocks as a way to adapt to nights, while NIOSH notes that most night workers switch back to a daytime schedule when they are off.

How much time off should follow a run of nights?

A 2006 workplace safety article suggests at least 24 to 48 hours when someone rotates off nights. NIOSH's training suggests two rest days after three consecutive 12-hour shifts.

Do longer night shifts change the answer?

Yes. NIOSH says night shifts of 8 hours or less are better tolerated, and the 2020 consensus pairs its 3-night limit with night shifts of 9 hours or less.

How many night shifts in a row?

Updated October 8, 2026 · 3 min read

Most guidance favors short runs. A 2020 consensus of shift work researchers recommended no more than 3 night shifts in a row, and in a 2006 risk index the 4th night carried 36% more estimated injury risk than the 1st. ACEP's statement for emergency physicians recommends either single nights or fairly long blocks of nights, and warns against very long stretches.

What the guidance says

Guidance on runs of night shifts
Source	What it says
2020 consensus of 15 shift work researchers	No more than 3 night shifts in a row, at least 11 h between shifts, night shifts of 9 h or less
NIOSH training for nurses	Keep consecutive nights to a minimum on rotating schedules; at night, shifts of 8 h or less are better tolerated
ACEP policy statement	Single nights or fairly long blocks of nights; avoid very long stretches of consecutive nights
Workplace safety article, 2006	At most 4 nights in a row before a couple of days off; no more than 48 h of night work a week

How risk builds over a run

Successive night shifts

1st night: 1.00
2nd night: 1.06
3rd night: 1.17
4th night: 1.36

Successive day shifts

1st day: 1.00
2nd day: 1.02
3rd day: 1.07
4th day: 1.17

Estimated relative risk of injuries and accidents on the 1st to 4th shift in a row, from a 2006 risk index. Nights rise to 1.36 by the 4th night and day shifts to 1.17; 1.00 is the first shift of each kind.

The index pooled published studies of injuries and accidents at work, so it estimates workplace incident risk, not clinical error. Risk climbs faster across nights than across days, and NIOSH's summary of the same estimates puts the highest risk on shifts that are both long and at night.

Two ways ED groups schedule nights

ACEP's companion paper on circadian rhythms describes two opposite approaches:

As few nights in a row as possible. The body clock stays on a daytime pattern, at the cost of working every night at the wrong time for it.
Block nights. One physician works nights for a long stretch, for example two months, while the others work only occasional nights. In a group of six, each person's block comes around once a year.

The paper warns that a middle-length run gets the worst of both: long enough for the body to start adjusting to nights, then a switch back to days. Blocks also depend on keeping a night pattern on days off, and NIOSH notes that most permanent night workers switch back to a daytime schedule when they are off. Where a group does use dedicated night workers, NIOSH advises measures to protect patient safety on the first night back after days off and from 02:00 to 06:00.

A worked example

A department staffs one 8-hour physician night shift every night, about 30 a month, shared among 10 physicians: 3 nights each. Here are three ways to place them, scored with the 2006 index (a first 8-hour day shift is 1.00, a first night 1.06).

Three ways to place 3 nights in a month
Pattern	Highest index value	Returns to days
One run of 3	1.23	1
A run of 2, later a single night	1.12	2
Three single nights	1.06	3

All three stay within the consensus limit of 3. Single nights keep every shift at the lowest index value but mean switching between nights and days three times; one run of 3 means one switch, with the 3rd night 0.17 higher on the index than the 1st. Whichever you choose, put time off after the run: the 2006 safety article suggests at least 24 to 48 hours when someone rotates off nights.

My hours flags a 3rd night in a row and can score each shift with the same 2006 risk index. To try the numbers on your own pattern, use the shift fatigue risk calculator.

Common questions

Is it better to work nights in a block?: It depends on whether the person keeps a night pattern on days off. ACEP's companion paper presents blocks as a way to adapt to nights, while NIOSH notes that most night workers switch back to a daytime schedule when they are off.
How much time off should follow a run of nights?: A 2006 workplace safety article suggests at least 24 to 48 hours when someone rotates off nights. NIOSH's training suggests two rest days after three consecutive 12-hour shifts.
Do longer night shifts change the answer?: Yes. NIOSH says night shifts of 8 hours or less are better tolerated, and the 2020 consensus pairs its 3-night limit with night shifts of 9 hours or less.

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