How to Make Penicillin at Home (Just in Case SHTF)

Last Updated: August 4, 2022

One of the hottest topics in the prepper and survivalist world is how to make penicillin at home.

Considering how expensive healthcare is, I wouldn’t be surprised if there aren’t some DIY types also wanting to learn how to make penicillin.


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Because penicillin is “just mold bread” and was discovered by accident, it might seem pretty easy to make penicillin. Yes, it is – but it is really hard to make penicillin safely. If you want to learn how to make DIY penicillin, here’s what you need to know.

Even in SHTF Situations, Homemade Penicillin Probably Isn’t a Good Solution

Before I even get into the (complex) instructions on how to make penicillin at home, I want to emphasize that it isn’t as straightforward as many prepper sites would have you think.

  • Penicillin doesn’t treat superbugs: Antibiotic-resistant bacteria is a huge problem. Already many bacterial strains are resistant to penicillin. So, don’t count on penicillin to save you from every infection!
  • Penicillin doesn’t treat all infections: Penicillin can be used in many throat, respiratory, and skin infections. It won’t treat tooth infections or UTIs (amongst others).
  • It requires strange ingredients: Most people won’t have these things at home if SHTF.  That’s an insane level of preparedness. Even if you do have the supplies, it’s still very complicated to safely make penicillin.

When Would I Recommend Learning to Make Penicillin?

I think learning any skill is a good use of time. However, I personally think that this one only makes sense if you plan on becoming an expert. I mean REAL EXPERT.


Because you could make penicillin as a SHTF bartering item. You’ll become much more valuable to your survival community if you know this too. Otherwise, you are spending a lot of time on this skill when simpler alternatives exist.

Alternatives to Homemade Penicillin

Most doctors won’t give out prescriptions for antibiotics “just in case.” Even if they did, those antibiotics can be really expensive!

A better alternative is to use fish antibiotics, which currently don’t require a prescription, are cheap, and easy to get.

Recommended ReadingWhat you need to know about fish antibiotics for humans

But, just in case you still want to learn to make penicillin, here are the instructions!

Good luck!!!

Step 1. Isolating Penicillin Bacteria


Put a piece of bread, cantaloupe, or citrus fruit in a container in a dark place at 70 degrees F. It should be in a closed (but not airtight) container. It helps to add a few drops of water to the container and leave all but one corner closed to keep in moisture.

It can take weeks for the mold to start growing. Hopefully, you aren’t trying to treat gangrene with your DIY penicillin because your patient will likely be dead before you get any usable spores.

The bread or fruit will start getting a gray mold. This gray mold will eventually turn a bluish-green color. This is the mold that you want for making penicillin!

Note: You’ll want to use homemade bread because most commercial bread contains additives to inhibit mold growth.

Step 2. Re-culturing the Penicillin

bread mold aka penicillin

The greenish-blue mold you grew contains penicillin. Some people call this mold “natural penicillin” and say you can use it immediately.  Unfortunately, this isn’t the case.

Does NOT Work: 

  • Rubbing Mold Onto a Wound: Rubbing penicillin mold onto a wound might treat surface bacteria, but won’t help much if the bacteria has already spread into the bloodstream.
  • Drinking Mold Tea: The penicillin derived directly from mold is very sensitive to stomach acid. If you drink it as penicillin tea, it will be destroyed before it makes it to your bloodstream. The only way to make this penicillin work is to inject it (not recommended!).

To get the benefits of penicillin from mold, it has to be further cultured.

Re-Culturing Penicillin

All links go to the product on Amazon for your convenience.

  • Thinly slice 200 grams of unpeeled potatoes.
  • Put the potatoes into a 1-liter mason jar and fill with distilled water. Screw on the lid tightly. Put the entire jar into a pot of boiling water. Boil for 30 minutes.
  • Once it cools a bit, open the jar. Strain the contents through a cheesecloth (sterilized lace curtains work in a pinch). Catch the liquid! This is the “broth” that you need.
  • Add 20g of glucose (aka dextrose) to the broth. If you don’t have glucose, plain sugar will work.
  • Add 20g of agar to the broth. If you don’t have agar, then plain gelatin (not Jello) will work. Note that the agar isn’t going to completely dissolve. That’s okay.
  • Add distilled water until the total volume is 1 liter.
  • Pour the broth into wide, flat jars with a sealable lid. Basically, anything that could work as a petri dish. If you actually have Petri dishes, then use ‘em!
  • Cover the dishes immediately to prevent microbes from the air from getting into them.

Step 3. Streaking Your “Petri Dish”

Now it is time to move your penicillin mold spores to your “Petri dishes” that have the potato broth in them.

There is a very specific method that scientists use for growing cultures. It is called “streaking.”

  • Get a thin piece of wire. Bend the tip into an oval shape.
  • Sterilize the tip of the wire in a flame. It should be red hot.
  • Dip the hot wire into the potato broth to cool it down (so the heat doesn’t kill your penicillin spores).
  • Now touch the wire tip to the greenish-blue penicillin mold.
  • Make three lines on your petri dish. This is where the colonies of penicillin will start growing.

Step 4: Let Your Penicillin Grow

penicillin in petri dish

Keeping it covered, let the penicillin grow in your DIY Petri dishes for about a week.

Penicillin is a yellow color.

However, other species of bacteria can also be yellow, so it is hard to tell for sure that you got penicillin without a trained eye and a microscope.

Step 5: Fermenting Your Penicillin

Here is where things get a bit complicated. You need to ferment your penicillin spores so they reproduce in huge numbers. Otherwise, it will be like trying to put out a forest fire with a bucket of water.

At most prepper websites, they tell you to get a bunch of weird ingredients like potassium monophosphate and sodium nitrate. That method works – but I doubt you will find those things laying around when SHTF.

Here’s a simpler method of fermenting penicillin.


These ingredients are all available on Amazon (click the images to view prices)



  • Sterilize the flask in the oven at 315 degrees F for one hour.
  • Put 1 tsp each of glucose, yeast, citric acid, milk powder, and sea salt into your graduated cylinder.
  • Fill the cylinder with water until it reaches the 100ml mark.
  • Pour the contents into your flask.
  • Put the lid on and shake until the contents are dissolved.
  • Add your penicillin cultures to the flask. Make sure you are using sterile methods, such as using a sterilized metal loop to add the cultures!
  • Cover the flask with sterilized aluminum foil. This will keep unwanted microbes out of the flask while still allowing for air flow.
  • Let the flask sit for at least 7 days but no longer than 14 days.


Penicillin cultures growing
This is what penicillin looks like growing in a glass flask.

Step 6: Extracting the Penicillin

After a week, you’ve got fermented penicillin in the flask.

You’ve got to get out all of the other ingredients before you can use it though.



  • There are going to be solid parts in the liquid. You need to separate these from the liquid. The liquid is the part which contains the penicillin, so you want to hang on to it!
  • Strain the penicillin liquid through a coffee filter or sterilized cheesecloth. Catch the liquid in a sterile container.
  • Now you need to adjust the pH of the penicillin. Add a drop of hydrochloric acid and then test the pH. It will probably be a pH of around 5 when you start. Keep adding drops and testing until you get a pH of 2.2.

In theory, you could use this extracted penicillin now. However, the penicillin is very unstable.

You’d have to use it right away. Considering that most infections need multiple rounds of antibiotics to treat, your whole efforts would be for nothing.

Thus, you have to do the fairly complicated and scientific step of further extracting the penicillin.

Step 7: Further Extraction

Ethyl acetate is used to completely extract pure penicillin.

The penicillin dissolves into the ethyl acetate. Then the ethyl can be evaporated, leaving you with pure penicillin.



  • Chill ethyl acetate in a freezer.
  • Mix the cold ethyl acetate and penicillin liquid in a separator funnel.
  • Shake them together for 30 seconds, then allow them to separate again. The ethyl acetate will sink to the bottom.
  • Open the separator funnel and allow just the ethyl acetate to slowly drip out into a sterile collection container (a mason jar works for this).
  • Now add potassium acetate to the ethyl acetate. You’ll need about 1g of potassium acetate for each 100ml of solution you have.
  • Leave the solution uncovered in a ventilated area. The ethyl will evaporate, leaving behind penicillin.

Using Your Homemade Penicillin

You’ll note that we started with about 100ml of fermentation. From that amount, you’ll probably only get about 100mg of penicillin.

Considering that the penicillin dosage for treating strep throat is 125-250mg taken every 6-8 hours for 10 days, you’ll need a lot of homemade penicillin to treat an infection!

A Better Solution?

I still think that knowing how to make penicillin is a good skill to have, but I wouldn’t bother until you’ve learned the core medical essentials.

Prevention is best, so take your first aid skills to the next level, learn how to treat a wound so it doesn’t get infected and consider growing a medicinal herbal garden.

And if you do master the science of making antibiotics at home, then let me know — I’d love to have you on my survival team. 😉

131” (CC BY-NC 2.0) by nsmithtnz
The Mold Rush” (CC BY-NC-ND 2.0) by Los Alamos National Laboratory
“Von Henry Mühlpfordt – Eigenes Werk, CC BY-SA 3.0, LinkBy Adrian J. Hunter
งานของตัว, CC BY-SA 3.0, Link

Leave a comment

    • Hi Julie,

      These “fish” antibiotics aren’t actually meant for fish. The sellers know that people like preppers want to get antibiotics without a prescription so they exploit a loophole in the law which allows them to market antibiotics for fish – even though they are the same pills for humans. Right now, the FDA does not require a prescription for fish antibiotics.

      We have a post about it if you want to read more –

      • i found this out years ago while treating some pet fish… it smells a bit but it worked the same and was so much less expensive in the late 90’s and no prescription necessary… loved going around the med-establishment

        • The question is, why did you have a tooth root infection? If you don’t treat the underlying reason that bacteria was able to get inside your tooth then you will get your tooth infection back again. But next time the bacteria will be resistant to the antibiotic class that you used with your fish antibiotics because 3 days is not long enough to kill every bacteria. Next time you have a tooth infection just go to the dentist!

          • agreed, people need to understand that every time someone does this or stops taking there perscription , ect, in make what ever they are infected with stronger.Creating super bugs that are resistant to antibiotics is not good , and becoming a major problem.. people think covid is bad , pffft..

  1. Hi there
    there are many kinds of culures media wich can be used to culture the Penicillium like saboraod dextrose agar or broth.
    That could be more helpful.

  2. We absolutely do use penicillin drugs in dentistry- in fact the first line (top choice) is Amoxicillin. Which, incidentally can also be used for UTIs, though it’s not first choice.
    Note: in dentistry we use antibiotics to bring a bacterial infection under control in order to be able to numb the area before a root canal and make it safer to do the procedure. It’s not an end in itself- the insides of the tooth or the tooth itself must be removed or the infection will return. In an shtf situation keep your teeth clean; don’t graze; use fluoride; and wear a hard night guard if you clench or grind (prevents fractures and broken down dental work). If you get an abscess, in an shtf situation, it’s probably best to extract. And take penicillin!

  3. Intersting! But long process and a lot to buy, unless you ”borrow some” in your lab at work!
    First formation as Chemist, and now family physician, this would be fun for me!
    Penicilin is still used in dentistery, by physician during week-ends, though others molecules with less resistance are used if more sévère. But patient wants pain killer and are anxious.
    Then dentist sees the patient somewhere during week. Occasonnaly, after receiving sensitivity of urine culture, pénicilline is used for some sensitive gut bacteria in urinary tract infection.

  4. So in the article it says to add these things to the cylinder then addwater to 100ml. How much of each thing?? This article was so very vague. Then there were things like ethyl acetate… so where do you get that when its a SHTF time? Can you make it? How?
    I think maybe a good article would be more specific & try to use the same stuff people might have laying around their house or something you dont have to order off of amazon, being that when SHTF we probably wont have much luxury.
    Disappointed with this article

    • Is this a serious comment? You can’t expect to make penicillin from stuff you have lying around in your home. The article goes into some depth and clearly states that this is a complex and somewhat unrealistic endeavor for all but the most advanced and organized prepper. For the vast majority of people I would strongly suggest looking at alternatives. You could look at these natural antibiotics or stockpile some fish antibiotics.

  5. Personally,,as someone w/lymes,,,,,,I wish everyone would keep their mouths shut,,,,,for all of us ADULTS know,,,,,if folks keep talking about this on the web,,,,,,thee good ole corrupt dea will make it illegal to buy fish medicine,,,u all know this to be true..If the public finds anything that they can get THEMSELVES,, god forbid we think for ourselves,,,”they” will take it away from us or make it illegal, Sooo please,,,,,,shut up ABOUT THIS,,,KINDLY,,,mw

    • I kinda see your point, but it is human nature to share information and try to help each other. That is our ethos and that is what we will continue doing.

  6. Good article. I praise the author for giving enough details to make it an interesting read, but also excluding enough details to prevent idiots from trying this at home!

  7. Please specify how much penicillium culture you added to the 100ml solution. The 1 tsp of each of those ingredients seem specific to react with a certain amount of the penicillin to get fermented penicillin.

    • Add all of the cultures from the 3 streaks in the petri dish. The penicillin will “eat” the ingredients and grow. The more you put, the faster you get a large amount of usable penicillin. Temperature will affect also how fast the cultures grow – hence why you let it grow for 7 to 14 days. In a lab, they would test the concentration, purify, etc. This is really only for a SHTF last-resort since it’s very difficult to do perfectly! I would recommend alteratives, like talking to a doctor about getting you an emergency supply of antibiotics or looking into fish antibiotics. However, you can still try DIY penicillin as an experiment in case you ever really need it.

  8. Since penicillin is sensitive to stomach acid I wonder if reducing or neutralizing said acid would help you skip the last steps. Like taking bicarbonate or antacid prior to ingesting the liquid form.

  9. Some forty years ago I was reading about the history of penicillin. According to the book they decided to find wild penicillin bacteria again but it took a long time to find and efficient one. If it is true, than the description above might not work. Can you please give your opinion on that?

    • I’m not enough of an authority on the topic to give an opinion, but it does seem plausible. In any case, there’s a LOT that can go wrong when trying to make your own penicillin. This is the type of info that’s good to have on hand in case SHTF but hopefully we will never, ever need to use!

  10. I bought a penicillin bacteria culture online. It cost me $20. It’s the most effective strain. I’ve been working with it for about a month. Ive had little success with the fermentation process described here so I made my own. For ever 200 ml of distilled water add 12 ml of 100% saturated water with 16-16-16 fertilizer. 3 TSP of lactose monohydrate. 1/3 TSP of glucose monohydrate. Stir until dissolved. Add your culture. Aerate with a fish tank air stone. Then wait 12 days. The culture will grow fast. Soon you won’t even be able to see through the solution.

    Follow the rest of the steps. With one exception; the acetate will float on top, not sink to the bottom.

    Cheers and good luck!

  11. It was a Sunday. on a trip to Washington State driving down the highway in the middle of nowhere I have suffered a tooth abscess. Pain is unbearable and adjust minutes had grown at Large as a tennis ball. As luck would have it I was driving by feed store. Amoxicillin by the gallon for pigs $100. Best Buy in my life.

  12. Please be aware.. some ppl are allergic to Penicillin. Those that have celiac’s disease should not take it either.


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