The world is a hard place to live in, more than just hunger and thirst, danger lurks everywhere and you should be afraid because death is horrible.

Here are some of the things you will have to look out for when surviving in TFC with Medicinal, all of which will have specific medicine to fight it:

When you die, your health will be at 20% and your hunger at half.
When you die, your nutrition stats won't be at half, but close to 0.
When you die, your items will be destroyed completely.
After you die, you will not spawn in your comfy bed, but randomly scattered around it in a radius of 1000 blocks (configurable)
After you respawn, a sickness will befall you, death sickness, preventing you from mining, building or fighting for an entire Minecraft day
The dust in mines will stress your lungs, making it harder to move and mine.
Uncooked meat as well as cooked meat that isn't wood grilled (on an iron grill) thoroughly can give you parasites, sapping your energy and hunger.

And now you are probably wondering why on earth would I want this addon then? Well for the challenge in avoiding or treating these ailments.

The following medicine can be made using this addon:

Death sickness antidote - cures death sickness when drank
Acuity Concoction - when you die while this effect is active, your items won't be destroyed and you will respawn in your comfy bed
Nourishing Concoction - resets your nutrition values to half across the board
Stomach Strength Concoction - protects you from meat parasites, hunger and nausea from aged drinks.
Lung Strength Concoction - protects your lungs from dust, letting you mine freely in caves, hold your breath underwater and swim faster
Rejuvenating Concoction - heals you fully in a minute
Keen Sight Concoction - lets you see in the dark
Health Boost Concoction - provides you with a boost of 40% hp for a limited duration
Cooling Panacea (TFC Ambiental) - cools you down 10 degrees for a while
Warming Panacea (TFC Ambiental) - warms you up 10 degrees for a while

But how do you make the medicine?

Flowers and plants in the world now have active properties:

Bright and red flowers have lively and healing properties
Blue flowers have mentally aiding properties
Yellow flowers have energising properties
Green plants (not grass) have soothing properties
Brown plants are rich in vitamins and minerals
Purple and pink flowers have strong fragrances
White flowers have powerful mixing capabilities, being used in all medicines.

Making the actual medicine:

Get yourself a mortar and pestle by crafting a ceramic bowl with a stick and flint.
Collect a nice variety of flowers, go exploring the new world if you have to and bring them home.
Crush the flowers in with the mortar and pestle by shift clicking it, putting the flower in and then right clicking it repeatedly.
The flowers will give you extracts that when crafted in a 3x3 will give you concentrates.
There are numerous catalysts to choose from that can be infused into a base concoction to be drunk.
Catalysts have different crafting recipes formed from different kinds of concentrates, use JEI for that.
Once you have the catalyst you want, you will need a Vial Heater that is crafted with some fire bricks and an alabaster filter.
Put the heater above a burning fire pit on the wall.
Craft yourself a glass vial with one piece of glass in the crafting table.
Find yourself some spiders underground and take their eyes and ferment them in some vinegar for a day.
Fill your vial with salt water from the ocean, put it in the vial heater and wait for it to boil (bubbles will form above it)
When the solution is boiling, add your fermented spider eye and at that point, the solution will start boiling more and more.
After one in-game hour your base concoction will be done.
Put any catalyst into it and boil it like the last few steps to obtain a drinkable concoction for you to use

TFC Medicinal