[KayJ]

https://sampwiki.blast.hk/wiki/OnPlayerTakeDamage
https://sampwiki.blast.hk/wiki/Attach3DTextLabelToPlayer

PHP код:

public OnPlayerTakeDamage(playerid, issuerid, Float: amount, weaponid, bodypart)
{
    if(issuerid != INVALID_PLAYER_ID) // If not self-inflicted
    {
        new
            infoString[128],
            victimName[MAX_PLAYER_NAME],
            attackerName[MAX_PLAYER_NAME];
        GetPlayerName(playerid, victimName, sizeof (victimName));
        GetPlayerName(issuerid, attackerName, sizeof (attackerName));
        new str[30];
        new Float:health;
        
        format(str, sizeof(str), "-%.0f HP\n%d HP Left", amount, GetPlayerHealth(issuerid, health));
        new Text3D:HealthLabel =  Create3DTextLabel(infoString, 0x00AE00FF, 0,0, 0, 20.0, 0, 1);
        Attach3DTextLabelToPlayer(HealthLabel, issuerid, 0.0, 0.0, 2.0);
    }
    return 1;
} 


Untested, let me know if problem persists.

EDIT: I saw that this will not delete the 3Dlabel once created so what you can do is; add timer to delete it.