MIRANDA LAMBERT has turned into a “drill sergeant” and ordered her hard-living hubby Blake Shelton to drop 25 pounds by summer!

The 5-foot-4 singer lost 35 pounds in just three months, whittling herself down to a sex-sational 105 pounds. And now she wants Blake to follow her lead.

Miranda has lowered the diet boom on her 6-foot-5 hubby, who a source says tipped the scales at 255 pounds last summer – 50 pounds more than he weighed when the couple tied the knot in 2011.

“Miranda is a one-woman diet police force,” revealed an insider. “Her confidence is soaring these days, and she told Blake he needs to shape up and drop the weight. She’s not taking ‘no’ for an an­swer.”

Miranda, 30, is especially con­cerned because her 37-year-old husband had a heart scare last year when he suffered chest pains, although, as is his style, Blake mocked the incident on Twitter.

Even though it was not his heart, the source says a worried Miranda told him: “‘Baby, I love you and I want to see us live a long life together.’

“She warned him that he was playing Russian roulette with his life by not dealing with his horri­ble eating and drinking habits and excess weight.”

Miranda then took swift action.

“She brought in her trainer, Bill Crutchfield, to work with Blake four times a week,” said the source. “Bill put him through a grueling, circuit-training workout that includes sprints, lunges and crunches. Miranda also enlisted Blake’s co-star on ‘The Voice,’ Adam Levine, asking him to drag Blake to 90-minute hot yoga classes a few times a week.

“She’s severely cut his caloric intake, too. Miranda hides alcohol and is limiting him to drinking beer just one day a week. Sometimes as a treat, she’ll make him a vodka soda, but with only half the alcohol.

“Miranda also cleared their homes of junk food and switched him from potato chips to raw almonds and rice cakes. For dinner, Miranda in­sists on salmon instead of steak, and she serves food on appetizer plates to trick Blake into think­ing he’s not on a hard-core portion-control diet.”

Under Miranda’s iron fist, Blake is consum­ing about 1,500 calories a day, said the source, “and he’s telling friends she’s a food tyrant.”

Pals say the effort Blake is making will help solidify the nearly three-year-old marriage, which has been rocked by his boozing and alleged skirt-chasing, as The ENQUIRER disclosed.

Miranda, who feels great since her own weight loss, is now focused on her husband’s health.

“Miranda is like a drill sergeant,” said the source. “It’s been an uphill battle, but she’s trying her best to change Blake’s eating and drinking habits.”