The 'Red Devils' had reportedly already agreed terms with both the player and his current club Porto after triggering his €20million (£17.4m) release clause.
Now the medical has been completed, the finishing touches can be made to the deal with sources claiming that the transfer will be announced soon.
Dalot would therefore become United's second signing of the summer after they confirmed the arrival of midfielder Fred from Shakhtar Donetsk on Tuesday afternoon.
The 19-year-old made his debut for the Portuguese club back in February and is regarded as one of the hottest defensive prospects in Europe.