This follows incidents in Kirkcaldy, Dunfermline and Kennoway at the weekend which saw five people hospitalised.
And police believe this spate of drug users needing medical attention is "more than just coincidence".
One man is still in a serious condition at Queen Margaret Hospital, while the other four, who were treated by emergency services, are now recovering.
Police are also warning that three types of drugs are being sold which may have caused adverse reactions when mixed with other drugs.
Fife Police drugs coordinator, PC Kenny Cameron, said: "While these incidents are spread across the force area we know drug suppliers can have extensive networks of contacts.
"Such a high level of incidence is unusual for Fife and we are concerned it is more than just a coincidence.
''Drug users must be aware of an added risk at this time and avoid the use of these drugs.
"Lives can be saved if anyone who witnesses a possible drug overdose contacts the emergency services immediately. Seconds are vital in such circumstances, and it is essential that immediate action is taken to help anyone who may be experiencing a drugs overdose."
PC Cameron added that the real concern was that drug users are mixing heroin with other drugs, including alcohol and benzodiazepines such as Diazepam.
"Taking individual drugs is hazardous enough, however, taking any form of substance, including alcohol, particularly in combination increases those risks considerably," he said.
In the first five months of 2006, there were two accidental overdose deaths in Fife, however, that number has increased to five deaths in the first five months of 2007.
Doctor Margaret Hannah, consultant in public health, added that there are now 25 trained overdose intervention leaders in Fife, who provide training to staff and drug users in managing overdose.
She said: "The leaders go around the drug agencies in Fife and explain what to do if someone has an overdose.
"They make sure people are aware of the recovery position, how to make sure they don't breath in their sick and other things that can potentially save lives.
"The people we are extremely worried about are those who don't use the drug services that Fife has to offer, and don't know this information, but we are working hard to get it out there.
"Our advice to drug users themselves is to use less than half their usual amount and don't take anything that looks different or unusual.
"Inject in the presence of someone who is not a user and seek help from our local services."