A directive to state and private medical facilities warned that any refusal to accept such patients was against the law and would be "followed up", the official news agency Irna reported.
The number of people contracting HIV in Iran has risen steadily in recent years.
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Before we can even fight the disease, the stigmas need to be removed and doctors need to get on board
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Iranian doctor
According to the latest official figures, 4,237 people have developed full-blown Aids and nearly 21,000 others are HIV-positive.
A major cause of HIV transmission is the use of infected needles, particularly in the country's jails.
"Although the figures of contamination (with Aids) in Iran are not high yet, the presence of this wild virus in society augurs of gloomy prospects", the directive signed by the deputy health minister said.
Taboo
A doctor involved in efforts to control HIV and Aids told the AFP news agency that the latest initiative was a "positive step" although there was "a long way to go".
"Before we can even fight the disease, the stigmas need to be removed and doctors need to get on board," the unnamed physician said.
The Health Ministry's directive also asked for "the all-out support of the nation and the country's health centres for Aids patients".
Correspondents say that people who contract Aids or HIV through sexual transmission are reluctant to seek medical help because of social taboos related to sexual relations in Iran.