Charities that support people with ME have warned against combining new specialist treatment for the condition with proposed services for long Covid.
The Health and Social Care Board is developing plans to help those still experiencing long-term health issues months after being unwell with Covid.
Some of the debilitating symptoms are similar to those reported by people with ME.
Myalgic encephalomyelitis (ME) is a chronic neurological condition.
The health board confirmed it was looking at the possibility of running ME specialist clinics alongside clinics for people with chronic fatigue symptoms "such as are experienced by some patients following Covid".
It added: "There are no formal proposals at present but this was discussed with ME patient representatives.
"The board is continuing to explore options with ME representatives."
The Office of National Statistics estimates that one in 10 people who contract Covid-19 will still suffer symptoms more than three months later.
There are more than 7,000 people estimated to be living with ME in Northern Ireland, which is the only part of the UK without a specialist.
That is in spite of two unsuccessful attempts to recruit an ME clinical lead since 2018, most recently last year.
Joan McParland, who runs the Hope for ME and Fibro charity from her home in Bessbrook, County Armagh, has lobbied for specialist ME services in Northern Ireland since 2011.
She is concerned that ME patients will have a longer wait for help if referred to the same clinic as people with long Covid.
Ms McParland, who has been living with ME for more than two decades, said: "To say that ME is long Covid is not acceptable because we know what ME is.
"It's classified by the World Health Organization, whereas the incidence, natural history and aetiology of long Covid symptoms are not known.
"In a 10-year campaign and promises after promises, we got the rug pulled out from underneath us when it was suggested we would be put into these fatigue/long Covid clinics with no ME experts.
"We are absolutely gutted and disheartened about the situation - no matter where we turn we hit a brick wall."
Dr Charles Shepherd, the ME Association's medical adviser, said the ideal situation was to have separate long Covid and ME clinics that share knowledge.
"There are overlaps where both conditions can be of help to each other but, if you join up the two, because of this enormous demand that there's going to be for the long Covid [service], the ME patients are going to be put to the bottom of the queue," he said.
"They really do need their own specialist service, just like the people with long Covid do."
Dr Shepherd said about a quarter of ME patients are severely affected by the illness, meaning they can be confined to their bed.
He said it was "scandalous" that Northern Ireland has no dedicated service when England has roughly one hospital-based referral service for every two million people.
He added: "We don't know how many people have long Covid at the minute. It's a tsunami that's arriving of another urgent need."