The HSE is urging people in Limerick to pre-book their appointments if presenting for Covid-19 tests.
It comes as HSE Mid West Community Healthcare, which operates test centres across the region, is now conducting more tests than at any other stage in the pandemic.
Over 43,000 tests have been completed last month alone.
In Limerick, over 6,100 tests were carried out last week at the Covid test centre in Ballysimon, while the first three days of this week saw an average of over 1,000 tests per day there.
This surge in demand means that walk-in testing cannot be accommodated and tests are only available by booking in advance.
People attending the test centres will be required to verify their pre-booked appointments upon arrival, and it may not be possible to facilitate testing outside their allocated time slot.
Members of the public can book appointments via the HSE website. Those who do not have internet access can seek a test through their GP.
All testing is free of charge and is available seven days a week.
Ellen Rush, Covid-19 Testing Lead with HSE Mid West Community Healthcare said: "Our staff are under significant pressure with the high number of people currently presenting for tests.
"We're appealing to the public to help us by booking their tests in advance, and by attending for their tests at the allocated time."
HSE Mid West is also urging people in Clare and Tipperary to book Covid tests online.
Over 5,900 tests were completed in Ennis in the last two weeks of October while 7,900 tests were carried out in Nenagh.
Chief Officer with the HSE Mid West Community Healthcare Maria Bridgeman said that in Limerick up to 1,000 people are being tested everyday.
Speaking on RTÉ's News at One, Ms Bridgeman said that people attending the test centre without first booking an appointment is slowing the process.
She said: "The demand is still very busy. At the moment, in Limerick, we are testing approximately up to 1,000 people per day and that increases further because we have a testing centre in Nenagh and in Ennis, Co Clare, as well.
"So our activity in Limerick is up to 1,000 tests a day and the request from us is to ask people to go online and to book the test, because it makes the system flow much easier for the people when they attend the test centre."
In the Midwest over the past fortnight there have been over 2,800 positive cases, 1,500 of these were in Limerick alone, Ms Bridgeman said.
Generally a person will be given an appointment within 24 hours, she said.
