Teigen said pregnant Markle’s experiences were “hitting too close to home” and warned that “these people won’t stop until she miscarries”.
The model tweeted: “This Meghan Markle s*** is hitting too close to home for me.
“These people won’t stop until she miscarries. F***ing stop it.”
Teigen lost a pregnancy last year and has spoken openly about how the experience affected her.
Teigen’s due date would have been last month, and the star spoke out about her grief and sadness over her miscarriage.
She wrote on Instagram: “He would have been here any day now - if he were like Luna and Miles, I’d probably be holding him as we speak.
“I am so full of regret that I didn’t look at his face when he was born. I was so scared of seeing him in my nightmares that I forgot about seeing him in my dreams.
“I hurt every day from that remorse.
“This month is a rough reminder and to be honest, I thought the worst was over but I guess life and emotions aren’t on any sort of schedule.”
Meghan and Harry have given an in-depth interview to Oprah, due to be aired on 7 March.
A statement on Wednesday said: “Accordingly our HR team will look into the circumstances outlined in the article.”
Meghan has denied the claims and said she is “saddened” by the allegations.
Oprah with Meghan and Harry will be broadcast on ITV in the UK on Monday 8 March at 9pm, the day after it is shown in the US.
In one trailer for the interview, Prince Harry tells Oprah that his biggest concern is “history repeating itself,” seemingly alluding to the media treatment of his late mother, Princess Diana.