Survival mode Survival mode is a unique gameplay mode in " Fallout 4 " with significant differences to other modes . Survival mode was added to the game for all platforms on March 29 , 2016 . It replaced the existing Survival difficulty , which was renamed to Very Hard . General features . Survival mode can be accessed in the options menu . Unlike Hardcore mode used in , Survival mode can be set before starting a new game . This mode also cannot be toggled freely . Once Survival mode is activated , turning it off will permanently disable it from being reactivated for that save file . In survival mode , autosave and manually saving from the menu has been disabled . The only means of physically saving the game is to sleep in a bed , on a mattress , or in a sleeping bag . The exit save function is still available , but is a temporary save that is deleted automatically upon loading . Additionally , the use of console commands is disabled . Ammunition now has a set weight , per rounds , based on the ammunition type . For example the 10mm round has a weight of 0 . 025 per round , where as the mini nuke has a weight of 12 . If one becomes over - encumbered , their Agility and Endurance will drop by 2 , they will suffer from Fatigue and they will take constant damage to their legs . Rather than permitting fast travel while over - encumbered , the perk Strong Back eliminates these negative effects . Further to this , carry weight for the Sole Survivor and their companions has also been reduced . Locations take 35 in - game days for non - cleared locations and 80 in - game days for cleared locations to repopulate enemies and loot , as opposed to the standard 7 and 20 days respectively . Additionally , the workshop ' s inventory has been restricted , which may affect the availability of production items . While fixed enemy locations have increased repopulation times , the occurrence of random enemy encounters is two days or less . < section begin = " summarytable " / > < section end = " summarytable " / > Travel and navigation . Fast travel is disabled , with the exception of entering the institute , which can only be entered via fast travel while they are an available faction . Being a member of the Institute however , will not allow one to bypass fast travel ' s elimination as the only outward teleportation point is the C . I . T . ruins . Alongside the changes to fast travel , the compass ' s range of detection has been significantly restricted to a manner of meters for locations of interest and completely removed for NPC detection , hostile or otherwise . Enemies will still show on the compass if they are quest targets , e . g . in the Taking Point or Randolph Safehouse quests . Combat . In combat , there have been several key changes . Firstly enemies have had their attack strength and overall health / damage resistances increased , resulting in more challenging battles . Also the encounter frequency of higher level enemies has been increased , adding an additional layer of difficulty . Experience Points however , have been doubled . Additionally a new perk , Adrenaline , is automatically applied to the Sole Survivor for every five enemies they kill . This perk gradually increases up to a 50 % increase in damage . Health and well - being . Prior to survival , only " < nowiki > ' < / nowiki > " hardcore mode made food and drink a necessity . The Sole Survivor must remain hydrated , eat periodically and have a regular sleep cycle in order to survive . Failure to manage one ' s well being will result in negative effects such as Fatigue , Hunger and Thirst , reducing maximum AP . Additionally one can contract an illness from various sources , such as over sleeping on a mattress or from use of medicinal items . Additionally sleeping in a bed for less than 7 hours no longer heals Hit Points ( HP ) . Furthermore , the healing rates of restorative items are significantly slowed and the use of medicinal items such as Stimpaks , RadAway , and chems can result in thirst and in some instance cause the Sole Survivor to become ill . However , visiting a doctor for purposes of restoring health , removing rads , and curing addictions still carry no side effects . If one is crippled in any form , this no longer recovers with time and must be rectified with a stimpak , by sleeping in a bed until the Sole Survivor is well rested or by visiting a doctor . The third rank of Adamantium Skeleton however , largely negates this effect , as it makes the Sole Survivor ' s limbs immune from the effects of crippling . When downed in combat , companions will no longer heal themselves automatically and thus require a stimpak to recover from their injuries . If left unattended , they will leave the Sole Survivor ' s travelling party and return to their most recent settlement to recover . Generic robotic companions constructed in the robot workbench as part of the " Automatron " add - on function differently to other companions . As they no longer hold essential status , they will explode on death , becoming unrecoverable . Wellness . There are five stages in each category of wellness that span in - game hours . The increasing thresholds for each form of wellness are on a curve , for example , it takes about 6 hours to go from well - fed to peckish to hungry , then a further 12 hours to go from hungry to famished . The following table shows the approximate times that it takes for a character to go from completely satisfied to the listed condition in each area . In - game time is expressed in " hours " and real - time is expressed in " minutes . " These effects can be sped up when using certain items . Stimpaks and other drugs inducing dehydration , RadAway causing hunger , etc . Thirst . Thirst will negatively impact the Intelligence , Luck and Perception stats , making it more likely one will drink directly from manual water pumps , water fountains and open water sources such as puddles and rivers . Drinking from irradiated sources has the possibility of afflicting one with an illness . As a means of ensuring one has a steady supply of water , the Sole Survivor can now fill empty bottle s with dirty or purified water . Dirty water is obtained from sources such as rivers , puddles or ponds . Purified water is obtained from water pumps and water fountains . Hunger . While the Sole Survivor is hungry , the healing and bonus properties of food consumption is suppressed until enough is consumed to make the survivor " well - fed . " However , eating something that grants a bonus ( e . g . the + 1 Agility of deathclaw steak ) while hungry will remove the bonus if it is already active . For example , eating a deathclaw steak while not hungry to gain the bonus , then becoming Peckish , then eating a second deathclaw steak to become well - fed will negate the + 1 Agility bonus and would require eating a third deathclaw steak to regain it . The amount of food that must be eaten to do this is relative to its quality ( or price ) , i . e , a ribeye steak satisfies hunger more than a grilled radroach . Certain foods , such as soups and certain crops , will satisfy both hunger and thirst . The Cannibal perk has a special interaction called Dark Craving when eating a corpse is used to satisfy hunger . Sleep . Sleeping for at least one hour on any bed , mattress or sleeping bag will save the game , and remove any Fatigue the player character has developed from being tired . The Sole Survivor cannot sleep more than 3 hours in a sleeping bag or a tent , and more than 5 hours on a mattress . To sleep for longer amounts of time , it is required to use a real bed . Attempting to sleep for longer than these times will result in one waking up at the time threshold and any further attempt to sleep may result in an illness ( e . g . parasites . ) Sleeping for seven hours or more allows one to recover health and if sleeping in a bed as opposed to a mattress or sleeping bag , will ensure one is well rested and minimizes risk of illness . Being only asleep for one hour in any bed , even at a workshop settlement , will still grant a high risk for illness , in particular parasites . Lethargy , insomnia and weakness are common . Consuming caffeinated drinks such as Nuka - Cola will delay the need to sleep for some time . " Note : The in - game / real - time data in the tables above are approximations only . "