What's on the exam
Vision (46 CFR 10.305): deck applicants need correctable vision of at least 20/40 in one eye and uncorrected vision of at least 20/200 in that same eye; engineering, radio, and tank-vessel applicants need 20/50 corrected. Color sense is checked without color-sensing lenses using pseudoisochromatic plates (e.g. Ishihara), a Farnsworth lantern, or a Titmus tester. Hearing (46 CFR 10.306): an unaided audiometric threshold of 30 dB or less in at least one ear (averaged over 500, 1,000, and 2,000 Hz), or functional speech discrimination of at least 90% for an original credential (80% on renewal) at 65 dB. Blood pressure is recorded — sustained readings around 150/90–160/100 and above typically prompt further evaluation under USCG medical guidance. A cardiac / neuro / respiratory screen and a medication review round out the form.
Who can sign
Under 46 CFR 10.302(b), any required test, exam, or demonstration must be performed, witnessed, or reviewed by a licensed medical doctor (MD or DO), a licensed physician assistant, a licensed nurse practitioner, or a USCG-designated medical examiner. The provider does NOT need to be USCG-affiliated, but they must hold a current US license to practise.
How long it's valid
The medical certificate's validity depends on the kind of service you do, not the credential you hold. Mariners serving on vessels subject to STCW get a certificate valid for 2 years (1 year if under 18). Every other mariner — which covers most OUPV/six-pack and Master less than 100 GRT operators on domestic, non-STCW routes — can be issued a certificate valid for up to 5 years (46 CFR 10.302). Renew the certificate before it lapses; the NMC will not issue or renew a credential against an expired CG-719K.
Common flags
Diabetes (insulin-dependent vs not), seizure history, sleep apnea, cardiovascular events, controlled substances. Most flagged conditions can still be cleared with documentation — it just takes longer at the NMC review stage.