There are no Covid-19 PCR tests available in 18 counties across the country.
The HSE's self-referral portal shows zero availability in numerous counties nationally, as demand for testing is still very high.
It comes as the Social Democrats are calling for testing capacity to be increase.
The party's co-leader Roisin Shortall said asking people to get tested if they've symptoms but not providing tests is counter productive.
"What ends up happening is people tend to plough on and hope it's just a flu or something like that."
3,666 cases of COVID-19 were detected yesterday, while 638 patients with the virus are in hospital - including 130 in ICU.