McDonald's customers queuing for their fix today may be devastated to learn their Big Mac or Quarter Pounder could lack lettuce.

The fast food chain posted to Facebook last night to apologise for a lettuce shortage at some restaurants.

"Due to demand, some of our stores have temporarily run out of lettuce. Our suppliers and delivery trucks are working hard to restock restaurants," the post said.

"You can still order your favourites, but for those stores that have run out they will be made without lettuce. Thank you for your understanding."

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McDonald's website says it uses iceberg lettuce in its classic burgers. The crunchy green heads are grown year-round, mainly in Bombay, on the southern edge of Auckland.

The chopped lettuce common in Macca's burgers comes from the heart of the iceberg head, which is crunchier and whiter than the outside.

There should be no shortage of icebergs in autumn, which is usually prime picking season, but instead is likely a logistical issue.

Vegetable growers have raised concerns they'll have a glut of greens on their hands in level 3 as markets won't be open, so they won't be able to sell their produce.

The fast food chain has seen massive queues as people drive up to get a taste of the burgers and chips they've been missing for the past month.

Food shops had a four-week hiatus as the country went into lockdown to stop the spread of Covid-19. Many including McDonald's gave their perishable produce to charity before alert level 4 kicked in.

When the lockdown lifted on Monday, desperate Kiwis lined up for hours to get their Macca's fix, with 300,000 burgers sold on Tuesday - one for every 16 New Zealanders.

Some resorted to breaking their bubbles when fast food stores reopened for contactless orders, with drive-thru queues at McDonald's and KFC causing traffic jams around the country.

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Many shops have a limited menu - there are no burgers at KFC and no sundaes at McDonald's, for example - while they get back up and running.

Staff are also subject to physical distancing rules under level 3, limiting how many people can work in the kitchen.