T.K. Carter died at his home after battling serious health issues … according to his family and authorities.

The actor’s older brother, Harold, tells TMZ … the 69-year-old had been dealing with multiple medical problems in the months leading up to his death — including diabetes and ongoing heart issues.

Law enforcement sources tell TMZ … T.K.’s family requested a welfare check last Friday after not hearing from him for a couple of days, and informed authorities T.K. had high blood pressure. Officers responded to his residence in Duarte, California — about 20 miles east of L.A. — where family members met them on scene.

We’re told authorities entered the home and found T.K. deceased. He was alone at the time, and it’s unclear how long he’d been there. His personal doctor agreed to sign the death certificate.

As of now, Harold says the family does not know T.K.’s official cause of death. He also mentions that when T.K. was found, he apparently suffered a head injury and was beside a marble table.

Harold tells us … “My brother was a very uplifting person, always funny. He was a good person. We miss him, he had a lot of friends and family. We will always cherish him. He had a relationship with God and his faith was very important to him.”

Carter’s career stretches back to the mid-1970s, with “The Thing” marking his big break. He went on to appear in films like “Runaway Train,” “Space Jam,” and “Domino.”