Daniele Bosio, the Italian ambassador to Turkmenistan, suffers from a kidney condition and blood sugar problems that may have been worsened by his stressful confinement in a crowded cell, a member of his family told AFP.
The 46-year-old diplomat was holidaying in the Philippines when he was arrested five weeks ago following a complaint by a children's advocacy group who alleged they saw him acting "inappropriately" with three homeless boys at a park near Manila.
"Of course, I don't want to risk his health condition...so I decided that it is best to grant his request for a medical check-up," state prosecutor Agripino Baybay told reporters.
Bosio was earlier detained in a tiny cell with dozens of other people at a police station about an hour's drive from the Philippine capital.
The prosecutor said the Italian would have to return to the cell after his treatment and attend more investigative hearings aimed at determining if there is enough evidence for him to be charged with a crime.
The notoriously slow Philippine judicial system means the proceedings could drag on for months.
Bosio's brother Andreas told AFP the diplomat, who was suspended from his post after his arrest, would consult a specialist in Manila.
His family insists he is innocent and he was only trying to help local street children when he was arrested.
They have described him as a frequent backpacker who even provided financial support to a children's school in the Philippines.