So in the item descriptions of stimpaks in various Fallout games, its noted that stimpaks stimulate cell regeneration and red blood cell production. This makes a lot of sense, since they're suggested to be a sort of battlefield first aid-- an 'apply to prevent bleedout' sort of item, boosting the system and stopping the worst of internal/arterial bleeding... but in a wide world of radiation, I see a more pointed purpose that also leads to some fascinating implications, as well as possible dangers of stimpak overuse.
See, our cells response to radiation is mass suicide. This is what happens when you get a sunburn. That redness, inflammation, and heat on your skin? Its not a traditional burn like you touched something hot. That is dermal cells going OH SHIT THOSE UV RAYS DAMAGED OUR DNA INSTRUCTIONS, WE'RE GONNA SELF DESTRUCT FOR THE GOOD OF THE BODY NOW. It is peacemeal tissue death-- thus why severe sunburns lead to peeling as whole sections of skin on the upper layers die off at the same time. Should these cells fail to execute this failsafe, this damage can lead to cancer because the part of a cell's instructions that tells them to respond to your body's signals on when to divide gets damaged.
This is what radiation does. It blasts off parts of our cellular instructions, and malfunctioning cells either kill themselves, are killed by the immune system, or start malfunctioning with incomplete instructions. Deeper ionizing radiation does the same, just to tissues deeper in the body, and ups the chances that a malignant error may occur.
Now let us consider the fact that Radaway doesn't restore health. It lowers radiation you've already picked up, detoxes your tissues... but it doesn't heal them. But the stimpak does
Because the stimpak kicks off cell regeneration-- to replace the cells lost to their own failsafe process.
Here's the thing tho-- unless stimpaks are filled with fucking Soylent, that means your body is using its own resources to repair damage, just faster... which means that anyone who uses a stimpak is gonna be FUCKING EXHAUSTED and SUPER HUNGRY once they're out of danger as their body burns through all internally available resources to heal damage and replace blood. And blood! Blood requires WATER, and you better be chugging it like a nutter who just found an oasis in the desert unless you want the ratio of red blood cells to plasma to be so off that it turns to sludge in your veins and causes cardiac arrest with the overstrain of the heart trying to circulate it.
And finally, lets talk folate.
Folate is an intensely important nutrient that humans usually pick up from leafy green veggies. Its abundant in kale and spinach, beet greens and asparagus. Why is it so important? Its a key ingredient in cell genesis-- the process of making new cells. Folate deficiency can lead to lethargy and body soreness as the body can't replace damaged cells at an optimal rate, and modern humans RIGHT NOW in the US tend to get not as much as they need, thus why its in pretty much any 'enriched' wheat product you've ever eaten. Check your pasta, your cereal, and your bread, most products that use enriched flour have had folate added.
Y'know what else has a butt ton of folate?
Pregnant persons who don't get enough folate tend towards having kiddos with a horrifying condition wherein the tissues of the back never seal over the spine, so the kid is born with their spinal cord and canal exposed. This results in death most of the time, so pre natal vitamins have a stupid amount of folate in them.
Conclusion-- people in Fallout who tend to get in a lot of firefights will pay top caps for folate supplements, and scavenged pre natal vitamins will sell for stupid amounts.
Secondary conclusion-- if a person is folate deficient, isn't eating well, or is dehydrated, a stimpak may actually do more harm than good.
Tertiary conclusion-- rad away stops the process of mass cell death in response to radiation poisoning, but you're still gonna be barfing up blood as your stomach gets rid of the cell lining thats already dead, and you're still gonna get ulcers and otherwise if you don't take the needed steps to replace those lost cells ASAP.