GMM is an add-on to group hospital and surgical (GHS) cover. When a hospital bill goes past the GHS limits, GMM pays part of the remaining eligible costs, up to its own overall limit.
Most GMM plans have a deductible, an amount the employee pays before GMM starts paying, and co-insurance, a share of the rest the employee pays, commonly 20%. That keeps GMM much cheaper than GHS.
Say a bill goes S$6,000 past an employee’s GHS limits, and the GMM plan has a S$1,000 deductible and 20% co-insurance. The employee pays S$1,000 plus 20% of the remaining S$5,000, and GMM pays S$4,000.
Insurers set GMM up in different ways. Some build major medical into their hospital plans, and some require the GHS and GMM plan levels to match. GMM is bought together with GHS, not on its own.