A HEALTH board has increased testing capacity to deal with an outbreak of syphillis.
NHS Lanarkshire warned that data suggests a "significant" number of individuals have not yet been diagnosed or treated.
The board said the potentially life-threatening sexually transmitted infection was mainly affecting young heterosexuals in North Lanarkshire.
If diagnosed early, syphilis can be easily treated with antibiotics.
However, untreated it can affect the heart, cause deafness or psychiatric illness, seizures and death.
Pregnant women can pass the condition on to their unborn baby, which can cause stillbirth or death of the baby shortly after labour.
A rise in syphillis cases was identified towards the end of 2012 and continued through 2013.
It comes after new figures showed hundreds of children, some as young as 12, are being diagnosed each year in Scotland with sexually transmitted infections.
NHS Greater Glasgow and Clyde had the highest number of diagnoses of Clamydia, with 112 cases in 2010, 121 in 2011 and 67 in 2012
NHS Lanarkshire said testing services would be challenged if the number of people being diagnosed with syphillis increases.
It is estimated that people with syphilis are three to five times more likely to catch HIV.
Dr John Logan, Consultant in Public Health Medicine, NHS Lanarkshire, said: "We would recommend that anyone who thinks they have symptoms of syphilis, or are otherwise at risk of infection, should be tested.
"For example, if you have a new sexual partner both of you should have a sexual health check-up, including a blood test, to make sure you are not putting each other at risk of syphilis, or any other sexually transmitted infection."
Lanarkshire runs quick check clinics where patients can be tested for syphilis and other sexually transmitted infections. No appointment is necessary.
Alternatively, sexual health clinic appointment are available by calling 0845 6187191. The line operates Monday to Friday from 9am to 4.45pm.
For more information, go to www.lanarkshiresexualhealth.org