You take something every morning. Maybe it is for your blood pressure, or your thyroid, or your mood, or your blood sugar. Now you want to try a dry fast, and nobody has told you the one thing you actually need to know first: do you keep taking it, or do you stop?
That question matters more than almost anything else about your fast, because there are two ways to get hurt and they point in opposite directions. One person keeps taking a drug that becomes dangerous the moment they stop drinking water, and ends up in real trouble. Another person, trying to be safe, stops a medication cold, and the stopping is what harms them, sometimes far worse than the drug ever could. Both of them thought they were being careful.
Most fasting advice online either ignores medications entirely or waves its hands and says "talk to your doctor" without telling you what to actually ask. That is not help, it is a shrug. I built the Scorch Protocol because conventional medicine kept doing exactly that to chronically ill people, hedging instead of answering. So here is the honest map: which of your medications actually matter, why they matter, and what to do about it.
Why a Dry Fast Changes the Drug Math
When you stop drinking, your body water drops, and two things happen to a medication. First, there is less fluid to dilute it, so the same amount of drug sits in a smaller space, which raises its concentration. This is not hand-waving. In the Russian absolute-fasting work, total body water falls about 1.6 liters over three dry days, and roughly three-quarters of that loss comes out of the extracellular compartment, the exact space most drugs distribute and get diluted in. Serum osmolality climbs from 285 to 302 mOsm/L over five days (Papagiannopoulos-Vatopaidinos et al. 2013). Your blood is measurably more concentrated, and whatever is dissolved in it rides that same tide up.
Second, your kidneys, which clear a large share of drugs from your blood, slow down when they are short on fluid. On a dry fast your urine output collapses: down 47 percent on day one, 70 percent on day two, 79 percent by day three, into true oliguria at around 320 mL over 24 hours, urine maximally concentrated (+80 percent). That is driven by antidiuretic hormone rising 191 percent and aldosterone 90 percent as your body clamps down to hold every drop. A drop in renal clearance is the quiet mechanism behind most medication trouble on a dry fast (Roberts and Buckley, 2018).
Here is the part to hold onto, because it is easy to catastrophize: this does not happen with every drug, and it does not mean your kidneys are failing. In a healthy person the kidney can actually filter better while dry, our own dry-fasting data shows it decongesting, not breaking. The danger is narrow. It matters for three kinds of drug. Drugs your kidneys clear rather than your liver. Drugs with a narrow therapeutic index, where there is not much gap between the helpful level and the harmful one. And drugs that themselves cut blood flow to the kidney. Learn to spot those three and you have most of the map. (Fasting also changes how your liver processes drugs, but not in one tidy direction, some pathways speed up and others slow, per Lammers et al. 2017, so "the fast slows your liver" is too simple to be useful.)
The One Class You Never Stop for a Fast: Benzodiazepines
If you take a benzodiazepine, Xanax (alprazolam), Valium (diazepam), Ativan (lorazepam), Klonopin (clonazepam), start here, because this is the most dangerous medication situation on this whole page, and the danger is the opposite of what people expect. It is not about taking it. It is about stopping it.
Benzodiazepines cannot be stopped abruptly. Your body adapts to them, and pulling them away suddenly can cause seizures, delirium, and dangerous swings in blood pressure and heart rate. This is not a mild rebound, it can be life-threatening, and the clinical guidelines are blunt about it: these drugs must come down slowly, never cold (Joint Clinical Practice Guideline on Benzodiazepine Tapering, 2025). So the idea of "pausing" your benzo to do a clean fast is genuinely dangerous. You do not pause it, and you do not skip a dose to keep the fast pure.
There is a second reason to take this one seriously while dry. Dehydration itself lowers your seizure threshold, so a dry fast and benzodiazepine withdrawal would push seizure risk in the same direction at the same time. That is not a coincidence to gamble on. On top of that, benzodiazepines are processed by your liver and several of them, diazepam especially, carry a long, unpredictable half-life, so their levels are among the hardest to reason about when your whole physiology is shifting under a fast. Between the withdrawal risk, the lowered seizure threshold, and the unpredictability, the answer here is the simplest on the page: if you are on a benzodiazepine, you do not stop it, cut it, or skip it to fast. Any change happens slowly, on a taper, long before any fasting calendar enters the picture.
Insulin and Diabetes Medication: Two Opposite Ways to Get Hurt
Diabetes medication is the other place people get into real trouble, and again it is because two failure modes point in opposite directions.
If you take insulin, or you have type 1 (insulin-dependent) diabetes, treat this as a hard stop: do not attempt a dry fast on your own. And just as important, never stop or skip your insulin in order to fast. For type 1 diabetes, stopping insulin is itself the emergency, not the fast. Without it your body floods with diabetic ketoacidosis even on an empty stomach, and dehydration makes it worse and faster. The evidence for this is clean and it is worth understanding, because it is the exact opposite of the intuition. In a monitored 25-hour fast of 56 type 1 diabetics, not one developed ketoacidosis, and the reason was that they kept their basal background insulin running the whole time (Type-1 Diabetes and Prolonged Fasting). The absence of food did not trigger runaway ketones. The absence of insulin would have. Read that as the warning it is: even a short, medically run fast required cutting insulin 50 to 75 percent, not stopping it, plus a glucose check every couple of hours. International diabetes guidelines put insulin-treated people in the highest-risk group for any fasting for precisely this reason (IDF-DAR, 2021). It is tempting to think "I am not eating, so I do not need my insulin." That is exactly the trap.
There is a second, opposite danger. If you keep taking a normal dose of insulin, or a sulfonylurea (the pills like glipizide, glyburide, and glimepiride that push your blood sugar down whether or not you eat), with no food coming in your blood sugar can crash dangerously low. In Ramadan fasting studies, symptomatic low blood sugar showed up in roughly one in five people on sulfonylureas (ADA Ramadan recommendations). And here is a detail that proves how tight the margin is: in the type 1 fast, the patients with the best control were the ones most likely to go low, because good control leaves less buffer. So a normal dose can be too much and holding your insulin entirely can be too little. The needle to thread is dose reduction, done deliberately, not a cold stop and not business as usual.
One more, because it is sneaky. The newer "-flozin" drugs (SGLT2 inhibitors like empagliflozin, dapagliflozin, and canagliflozin) can cause euglycemic DKA. Fasting and dehydration are known triggers, and the normal-looking glucose number is exactly what makes it dangerous, because it tells you nothing is wrong while something is. The FDA put a specific warning on these drugs for this (FDA, 2015). They come off before a fast, not during it.
If diabetes is the reason you are reading this at all, the fuller picture, including how a fast actually pulls fat out of the pancreas and lifts insulin resistance, is in dry fasting and type 2 diabetes.
When Being Dry Turns a Normal Dose Toxic
This is the dehydration group: the drugs that were fine yesterday and get riskier the moment you stop drinking. I want to be straight about where this list comes from. This is standard pharmacology, FDA labels and clinical guidelines, not some proprietary Scorch drug table. There is exactly one drug I will tell you I have personally flagged in my own patients, and it is a few paragraphs down. The rest of this you can verify against any drug label, and you should.
Lithium is the textbook case. Its safe blood level sits very close to its toxic level, and your kidneys handle lithium almost exactly like salt. This is where our own numbers make the mechanism concrete: on a dry fast your kidney goes into maximal salt-retention mode, urinary sodium excretion drops 87 percent by day three and aldosterone rises 90 percent as the body claws back every bit of sodium it can. Because it cannot tell lithium from sodium, it holds onto the lithium the same way, and the level climbs. The FDA's own lithium labeling warns specifically about dehydration and salt loss. Lithium and a dry fast do not belong in the same week.
The same shape shows up in a few other places worth knowing:
- Diuretics ("water pills"). Their entire job is to make you shed fluid and salt. Stacking that on a fast that already withholds water pushes dehydration and electrolyte trouble in the same direction. This is not just web knowledge, the same Russian dry-fasting literature we cite elsewhere lists diuretics, ACE inhibitors, and ARBs among its own contraindications. (Applies most to the common loop and thiazide types.)
- Blood pressure medication. Fasting and dehydration lower your blood pressure on their own, so a blood-pressure drug on top can drop it too far: the lightheadedness, the dizzy-on-standing feeling, the near-faint. To be fair, in healthy monitored volunteers blood pressure stayed stable on a dry fast, no fainting. But those people were not also taking a drug engineered to push it down. The stacking is the point.
- NSAIDs (ibuprofen, naproxen). These reduce blood flow to the kidney, which is the one thing a dehydrated kidney cannot spare. This is the entry that survives every caveat, because even a kidney that is filtering fine still cannot afford to have its blood supply choked. Taken while dry, especially alongside an ACE inhibitor or ARB and a diuretic, a combination clinicians literally call the "triple whammy," they can trigger acute kidney injury (Lapi et al. 2013).
- Digoxin, a heart medication with a narrow margin that leaves mainly through the kidneys, drifts toward toxic levels when you are dehydrated and low on potassium. Our own data shows potassium does drift down mildly on a dry fast (about 10 percent by day three as it shifts into the cells), which stays in range for a healthy person but is exactly the wrong direction for someone on digoxin.
Here is the one that is genuinely mine, not a textbook's. Valacyclovir, the common antiviral, turns nephrotoxic when you are dehydrated. I flag it in my own patients for a specific reason: kidney or lower-back pain during a fast is usually just an electrolyte-shift sensation, not organ trouble, and the fix is usually to walk it off, walking is a natural kidney massage. But if a patient is on a drug that becomes toxic to the kidney when dry, that same pain can be a real warning instead of a false alarm. That distinction is why the medication screen has to happen before the fast, not during it.
What's Actually Fine: The Other Half of the Title
The title promised you the "what's not dangerous" side too, because fearing everything is its own kind of wrong, and fear is what keeps chronically ill people from ever trying the thing that could help them.
Thyroid medication is the clearest good-news example. Levothyroxine (T4) and liothyronine (T3) are actually meant to be taken on an empty stomach. Levothyroxine is absorbed better fasting than with food (Colucci et al. 2013), and thyroid hormone acts slowly enough that small shifts in timing are well tolerated. This is one of the least troublesome categories to fit around a fasting window. Two honest points, though: the goal is never to skip doses, because skipping is the real harm here, not timing, and these pills are normally taken with a little water, so plan how you handle that on a dry day.
Beyond thyroid, a lot of ordinary once-daily medications can simply be timed to your refeed window rather than stopped. I am not going to hand you a blanket "safe list," because the safe answer depends on your specific drug and your specific body, and a printed list would give you false confidence. But the mental model is fair: most of your cabinet is a timing question, and only a handful are true danger.
Growth Hormone and T3: The Protocol's Own Rules
If you are working the Scorch Protocol, two of its own tools deserve a note, because their fasting interaction is specific and it runs against what most people would guess.
Growth hormone first. Here is something people do not realize: fasting is one of the most powerful natural growth hormone releasers there is. A five-day fast raised growth hormone output several-fold in the classic study (Ho et al. 1988), driven largely by rising ghrelin as you go without food. That is a feature, not a bug, and it is a big part of why fasting drives repair. But it is also exactly why you do not add injected growth hormone on top of a fast. Stacking injected hGH onto an already-surging system pushes it too high, into the territory of fluid retention, joint and carpal-tunnel aches, and worse insulin sensitivity. And there is a second, subtler reason. Injected growth hormone suppresses your own production while you are on it, working through IGF-1 feedback. So if you fast while still injecting, you actually blunt the very surge fasting is supposed to give you. This is the same feedback loop the protocol works around by adding a secretagogue later in the cycle to wake the pituitary back up. The sound move is to come off injected growth hormone and let your natural axis rebound before you fast, never to run it through the fast. Medical caveat: that sequencing is guidance to work out with the doctor managing your hGH, not a dose I can hand you here.
T3 is more individual, and I will not pretend it reduces to a rule. A fast suppresses your own thyroid output, our tradition's data shows T3 falling about 25 percent by day three, which is precisely why the protocol often restores T3 after a fast rather than running it through one. There are specific cases where a small amount of T3 through a fast makes sense and cases where it does not. That is genuinely per-person and supervised, one of the things the protocol adjusts rather than fixes by a formula. If your metabolism is the reason you are fasting in the first place, read up on the labs-look-normal version of this in cellular hypothyroidism and T3 therapy.
The Five-Minute Prep That Makes This Safe
Here is the concrete thing to do before you fast, and it is the actual practice I run every patient through, not a "talk to your doctor" brush-off.
Make a list of everything you take, prescriptions and supplements both. Then, for each one, flag three things: does my kidney or my liver clear it, does it have a long half-life so it lingers in me, and is it one with a narrow margin for error. In the Scorch Protocol, every patient's full medication and supplement list gets run through a screen against fasting before they start, upstream of the fast, never during it. That screen is exactly what catches the valacyclovir-shaped problems before they become kidney pain at 2am.
You can build your first-pass list with anything, including an AI assistant, to sort out which of your drugs are the long-acting, kidney-heavy, or narrow-margin ones. Two rules on that, because this is where people go wrong. Treat the output as a starting point, not an answer, it can be incomplete or flat wrong. And never stop, skip, or change a dose based on it. The list is a map, and the whole job of the prep is to walk into your fast already knowing which two or three of your medications are the ones that actually matter.
Where to Take This
If you are a curious self-experimenter, the payoff behind all this caution is worth understanding. Start with what a fast is actually doing under the hood in dry fasting, autophagy, and regeneration, see why fasting is your body's strongest growth-hormone signal in dry fasting makes GH stronger, and if you are a woman, the rules are different enough to have their own piece.
But if you are reading this because you are on several medications and dealing with the kind of chronic illness that put you on them, Long Covid, ME/CFS, thyroid or autoimmune disease, this stops being a general question and becomes a personal one. That is exactly what the Scorch Protocol is built to map, in the right order, and if you want your actual medication list looked at against your actual situation, that is what the members portal is for. Far better to have a real person help you sort the dangerous few from the harmless many than to guess at it alone, or to let the standard shrug scare you off entirely.
(This article is educational and is not medical advice, and it is emphatically not a reason to start, stop, or change any prescription on your own. If you take insulin, a benzodiazepine, lithium, or any narrow-margin drug, do not fast without direct medical supervision.)