You have taken the case, translated the patient's language into rubrics, run your repertorisation, and confirmed the remedy in the materia medica. The picture fits. You are confident in the similimum. And then the question every student eventually asks their supervisor arrives: "In what potency?"
It is a deceptively simple question with no single correct answer. The same remedy may be prescribed as a 30C, a 200C, a 1M, or an LM depending on the case in front of you, and the choice materially shapes how the prescription unfolds. Yet most teaching stops at remedy selection and treats potency as an afterthought, leaving practitioners to absorb the logic by osmosis over years of clinical exposure.
This guide closes that gap. It explains what potency actually is, how the scales relate to one another, and how to reason your way from a case picture to a potency and a dosing plan. The framing throughout is clinical: potency selection is a prescribing decision made by a practitioner in supervised or professional practice, grounded in Hahnemann's principles and the classical literature — not a fixed formula and never a self-treatment instruction.
What Does Potency Mean in Homeopathy?
In homeopathy, the potency number indicates how many times the remedy has been serially diluted and succussed, and the letter indicates the scale: X (decimal, 1:10), C (centesimal, 1:100), or LM/Q (fifty-millesimal, 1:50,000). A 30C, then, has passed through thirty steps of one-part-remedy-to-ninety-nine-parts-diluent, with vigorous succussion (forceful shaking) at every step.
Here lies the conceptual hurdle that catches every newcomer: in homeopathy, higher dilution corresponds to deeper and more far-reaching action, not weaker action. A 200C is not "more dilute and therefore milder" than a 30C in clinical terms — it acts more profoundly, reaches further into the mental and emotional plane, and tends to hold its action longer. Hahnemann's concept of dynamisation holds that the repeated dilution-and-succussion process develops the medicinal power of the substance rather than diminishing it. Whatever one's view of the mechanism, the clinical convention that follows from it is the practical knowledge a prescriber needs: potency is a lever on the depth and duration of the remedy's action, not on its raw chemical quantity.
What Is Posology?
Posology is the study of dosage — in homeopathy, the discipline that governs which potency to give, in what form, how much, and how often to repeat it. The word comes from the Greek posos, "how much", and the classical authors use it as the umbrella term for everything this guide covers: potency selection, the size and form of the dose, repetition, and the management of the remedy over the course of treatment. It is no afterthought in the literature — the dosage instructions Hahnemann kept reworking through successive editions of the Organon, culminating in the LM method of the sixth edition, are posological instructions.
The distinction worth holding onto is that potency is only one variable inside posology. Choosing a 200C answers the "how deep" question; posology also asks how that dose is delivered (dry globule, dissolved in water, plussed), how often it is repeated, and when it should be stopped or changed. Two prescriptions of the same remedy in the same potency can behave very differently in the clinic if the posology around them differs — a single dry 200C left to act for weeks is a different instrument from the same 200C taken in water daily.
Framing the question as posology rather than merely "which potency?" keeps the whole prescription in view. The sections that follow break the posological decision into its working parts: the scales and what they mean, the depth ladder from 30C to 1M, Hahnemann's three factors for matching potency to the case, and the repetition methods — single dose, measured repetition, and LM plussing — that complete the prescription.
The Potency Scales — X, C, M and LM
Three scales account for almost everything you will encounter in practice. Understanding how their steps differ is what lets you read a potency label and immediately know what kind of stimulus it represents.
Centesimal (C)
The centesimal scale dilutes 1:100 at each step and is by far the most widely used in classical prescribing. The familiar potencies climb the same ladder: 6C, 12C, 30C, 200C, then into the millesimal range — 1M (which equals 1000C), 10M, 50M and CM. The convention is worth committing to memory: 1M equals 1000C on the centesimal scale; 10M equals 10,000C and CM equals 100,000C — counter-intuitively, higher potencies act more deeply and for longer, not more weakly. When a colleague says "I gave a 200," they almost always mean 200C; the C is assumed in conversation.
Decimal (X / D)
The decimal scale dilutes 1:10 per step and is labelled X (or D in much of continental Europe). Decimal potencies — 6X, 12X, 30X — are encountered most often in lower-potency and combination contexts, and in tissue-salt-style prescribing. They progress more gently up the ladder because each step is a smaller dilution than a centesimal step, which is part of why they feature in gentler, more material-leaning prescriptions.
LM / Q (fifty-millesimal)
The LM scale (also written Q) dilutes at roughly 1:50,000 per step and was Hahnemann's final development, set out in the sixth edition of the Organon. LMs occupy a distinctive niche: they are gentle in delivery — administered in water, in ascending potencies, in small repeated doses — yet capable of deep action accumulated over a course of repetition. This combination of gentleness on each dose with depth over time is precisely why LMs became the preferred scale for sensitive, debilitated or heavily medicated patients in later classical practice.
30C vs 200C vs 1M — A Practitioner's Comparison
The heart of the potency decision lives in the contrast between the three potencies practitioners reach for most. The table below is the quick-reference map; the sections that follow explain the reasoning behind each row.
| Potency | Typical case type | Depth / plane reached | Repetition | Aggravation risk | Best suited to |
|---|---|---|---|---|---|
| 30C | Acute, low-to-moderate intensity; physical complaints | Physical with some emotional | Readily repeated | Low | The default teaching potency; beginners; provisional matches |
| 200C | Intense acute; clear constitutional pictures | Reaches more of the mental-emotional state | Repeated less often; a dose can act for weeks | Moderate | Confident matches; vigorous patients; deeper acute states |
| 1M and above | Deep constitutional and chronic work | Decisively mental-emotional / constitutional | Single or infrequent doses | Higher | Experienced prescribers; strong vital force; clear similimum |
A useful way to hold the whole comparison in mind: 30C is the standard starting potency taught in most homeopathy programs because it is versatile, moderate in depth and forgiving of imperfect remedy selection; 200C suits intense acute or clear constitutional cases and is repeated less often; 1M and above are reserved for deep constitutional work in single or infrequent doses.
30C
30C is the versatile middle-ground potency and the standard starting point in most training programmes for good reason. It reaches the physical plane and a degree of the emotional plane, acts dependably in acute and lower-intensity presentations, and can be repeated without great risk. Crucially, it is forgiving: if your remedy match is good but not perfect, a 30C is less likely to provoke a strong reaction than a higher potency would. For a student still building rubric fluency and materia medica confidence, that forgiveness is exactly the right safety margin.
200C
200C marks a step up in depth. It is the potency for intense or acute presentations with marked energy behind them, and for clear constitutional pictures where the remedy is well confirmed. It reaches further into the mental-emotional state than a 30C and is repeated far less often — a single 200C dose may act for weeks, so the classical discipline of "wait and watch" becomes important here. The corollary is that 200C carries more aggravation risk than 30C, which is why practitioners reserve it for cases where the match is confident and the patient has the vitality to respond.
1M and Above
The millesimal potencies — 1M, 10M, 50M, CM — are deep, broad and long-acting. They address the mental-emotional and constitutional level decisively and are given as single or infrequent doses. This is advanced territory: a high potency on a well-chosen remedy in a robust patient can produce a profound, durable response, but the same potency on an uncertain match or a fragile patient carries the highest aggravation risk of the three. As a rule, 1M and above belong to experienced prescribing, to clear similimums, and to patients whose vital force can sustain the depth of the stimulus.
How to Choose a Potency — Hahnemann's Three Factors
Hahnemann taught that potency selection depends on three factors — the patient's constitutional sensitivity, the nature of the disease, and the nature of the remedy — and that aggravations are commonly caused by too-high a potency or too-frequent dosing (Organon, 6th ed.). Those three factors translate into a practical four-step decision you can run on every case.
- Classify the case. Is this acute, chronic, or constitutional? An acute self-limiting complaint, a long-standing chronic pathology, and a deep constitutional prescription call for different potency strategies.
- Assess vital force and sensitivity. A debilitated, elderly, or heavily medicated patient — or one who reacts strongly to everything — favours a lower centesimal or an LM. A robust patient with strong reactive vitality tolerates higher potencies.
- Weigh the certainty of the remedy match. A clear, well-confirmed similimum tolerates a higher potency; a provisional or partial match argues for starting lower so that a reaction, if it comes, is manageable.
- Decide repetition and dose accordingly. The potency choice and the repetition plan are a single decision, not two — a high single dose and a low repeated dose are different strategies for delivering a stimulus.
From rubrics to remedy to potency, the workflow is one continuous chain of reasoning. After you repertorize the case, the potency decision is the natural next step — and the same case picture that produced the remedy also supplies the three factors that settle the potency.
Acute vs Chronic vs Constitutional
Case type is the first filter. Acute, vigorous presentations often suit a 200C; mild or self-limiting acute complaints are well served by a 30C that can be repeated as needed. Chronic cases on a first prescription frequently begin with a moderate potency so the practitioner can observe the response before escalating, while the deepest constitutional work — once the similimum is clear and the patient is robust — is where 1M and above come into their own. Mapping case type to potency in this way keeps the depth of the stimulus matched to the depth of the disturbance.
Patient Vitality and Susceptibility
The patient's vital force is the second filter, and it can override the first. A strong, reactive constitution tolerates and often needs a higher potency to be moved at all. By contrast, a sensitive, depleted, elderly, or pharmaceutically medicated patient may react sharply to a high centesimal, so a lower C or an LM — gentler on each dose — is the safer instrument. Because vitality and sensitivity are read directly from the consultation, it pays to assess vital force during case-taking rather than trying to reconstruct it afterwards.
Certainty of Remedy Selection
The third filter is your own confidence. When the repertorisation and the materia medica confirmation converge cleanly and the totality fits, you can prescribe with a higher potency. When the match is good but incomplete — when you have a working hypothesis rather than a confirmed similimum — the prudent course is to start lower. A 30C on a provisional match still gives useful clinical information without the risk a 1M would carry if the remedy turns out to be only partially correct.
From rubrics to remedy to potency — in one workspace. Repertorize across 14 repertories with semantic repertory search, cross-check your remedy's depth and sphere, then record the potency and dose in the case record so your follow-up comparison is grounded. Similia's AI case analysis surfaces candidate remedies from your consultation notes; you stay in control of the potency decision. Free tier forever.
Repetition, Single Dose and the LM Method
Choosing a number on a label is only half the prescription. How often the remedy is given — and whether it is given once and observed or repeated on a schedule — is the other half, and it interacts directly with potency.
Single Dose vs Repeated Dose
Classical practice with higher centesimals leans toward the single dose followed by watchful waiting: give the remedy, then allow it to act without interference, repeating only when the action is clearly exhausted and symptoms return. Lower potencies and LMs, by contrast, are designed for measured repetition. The principle behind both is the same — give the smallest stimulus that produces a curative reaction, and do not repeat while the remedy is still acting. Premature repetition is one of the classical causes of unnecessary aggravation.
Typical Repetition Rhythms
As a classically attributed rule of thumb — to be individualised to the case in front of you, never applied mechanically — lower potencies and LMs are repeated roughly one to three times daily, a 30C every two to three days, a 200C around weekly, and a 1M around fortnightly, with higher potencies given less often still. These rhythms are starting reference points, not prescriptions: the patient's response always governs the actual schedule, and a remedy that is clearly acting should not be repeated simply because the calendar says so.
Plussing and LM Dosing
The plussing method is a water-dosing technique central to LM practice and useful with centesimals too. The remedy is dissolved in water and succussed before each dose, very slightly altering the potency with each succussion so that the stimulus is gently modified rather than identical on every repetition. This allows frequent repetition without the accumulation problems that identical repeated doses can cause, which is exactly why plussing pairs so naturally with LMs in sensitive patients: it delivers depth over time while keeping each individual dose gentle and controllable.
Homeopathic Aggravation — Recognise and Respond
A homeopathic aggravation is a temporary intensification of symptoms following a dose, classically caused by too-high a potency or too-frequent or too-large a dose (Hahnemann). It is one of the most clinically important phenomena to understand, because the prescriber's interpretation of what happens after the dose determines the next move — and getting that interpretation wrong is how good prescriptions get derailed.
Aggravation vs New Symptom vs Return of Old Symptoms
Three distinct things can happen after a well-chosen remedy, and they must not be confused:
- A homeopathic aggravation is a short-lived intensification of the existing presenting symptoms, often followed by overall improvement — frequently read as a sign that the organism is reacting.
- A new symptom that does not belong to the case picture may indicate a wrong remedy, a proving, or an unrelated event, and calls for reassessment rather than waiting.
- A return of old symptoms — the reappearance of complaints the patient had years earlier, often in reverse chronological order — is read in classical practice as a favourable sign consistent with Hering's direction of cure, and generally calls for patience rather than intervention.
Distinguishing these three is a core clinical skill, and it depends entirely on having a complete, well-documented case to compare against.
How Potency and Repetition Choices Reduce Aggravation
Because too-high a potency and too-frequent dosing are the classical drivers of aggravation, the prescriber's main tools for minimising it are conservative potency and disciplined repetition. For sensitive, fragile, or uncertain cases this means favouring a lower centesimal or an LM, using the single dose where appropriate, and resisting the urge to repeat while the remedy is still working. The same case-reading that selected the potency in the first place — vitality, sensitivity, certainty of match — is what tells you how much aggravation margin you have, which is why these decisions cannot be separated from one another.
Choosing Potency in Your Repertory and Materia Medica Workflow
Potency selection is the closing link in a chain that runs case → rubrics → remedy → potency → dose, and it is far easier when the whole chain lives in one place. Once the repertorisation has produced your shortlist, cross-check the remedy in materia medica to confirm not just the symptom matches but the remedy's characteristic depth and sphere of action — a remedy known for acute, vigorous action invites a different potency strategy than one known for slow, deep constitutional work.
The case picture supplies the rest. Read the patient's vitality and sensitivity, weigh your confidence in the match, settle on a potency and a repetition plan, and — critically — record all of it in the case record. Potency, dose, date, and the reasoning behind the choice are exactly the data you will want at the follow-up, because the only way to learn potency selection is to compare what you prescribed against how the case actually moved.
Worked examples make the logic concrete. A remedy like Arsenicum Album, with its anxious, restless, fastidious picture and its strong constitutional dimension, might be prescribed as a 30C in a manageable acute state, a 200C where the constitutional picture is clear and the patient vigorous, or higher still in confident deep work. The same reasoning applies across the polycrest remedies every practitioner builds their early experience on: the remedy is chosen by similarity, but the potency is chosen by case type, vitality, and certainty.
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Frequently Asked Questions
What is the difference between 30C, 200C and 1M?
30C is a versatile low-to-medium potency suited to acute and physical complaints and readily repeated. 200C acts more deeply, reaching more of the mental-emotional state, suits intense acute or clear constitutional cases, and is repeated less often — a single dose can act for weeks. 1M is deeper still, decisively mental-emotional and constitutional, given as single or infrequent doses and reserved for confident, experienced prescribing.
What does 1M mean in homeopathy?
1M means 1000C on the centesimal scale — the remedy has passed through one thousand dilution-and-succussion steps. The millesimal notation continues upward: 10M equals 10,000C and CM equals 100,000C.
Which potency is strongest, 30C or 200C?
200C acts more deeply and for longer than 30C. The counter-intuitive principle is that in homeopathy higher dilution corresponds to deeper, longer-lasting action — not weaker action — so 200C is the more far-reaching stimulus of the two.
When should a practitioner use LM potencies?
LMs suit sensitive, debilitated, elderly, or heavily medicated patients, and any situation where gentle, controllable repetition is wanted. They are gentle on each individual dose yet capable of deep action accumulated over a course of repetition, which makes them well matched to patients who would react sharply to a high centesimal.
How often should a remedy be repeated?
As classically attributed guidance to be individualised per case rather than applied as a fixed rule: lower potencies and LMs roughly one to three times daily, a 30C every two to three days, a 200C around weekly, and a 1M around fortnightly. The patient's response always governs the actual schedule, and a remedy that is still clearly acting should not be repeated.
What is a homeopathic aggravation?
A homeopathic aggravation is a temporary intensification of the existing symptoms following a dose, classically caused by too-high a potency or too-frequent or too-large a dose (Hahnemann). It is distinguished from a genuinely new symptom (which may indicate a wrong remedy) and from a return of old symptoms (often read as a favourable sign of the direction of cure).
What is the plussing method?
Plussing is dissolving the remedy in water and succussing it before each dose, which slightly modifies the potency with every administration. This lets the remedy be repeated gently without the accumulation problems of identical repeated doses, and it is central to LM dosing in sensitive patients.
Is there a single best starting potency?
30C is the standard teaching default because it is versatile, moderate in depth, and forgiving of an imperfect remedy match. But there is no universal rule: potency should follow case type, patient vitality and sensitivity, and your certainty in the remedy selection.
Bringing It All Together
Potency selection is not a separate discipline bolted onto remedy selection — it is the same clinical reasoning carried one step further. The case picture that revealed the similimum also tells you the depth of the disturbance, the patient's vitality and sensitivity, and how confident your match is, and those are precisely the three factors Hahnemann named for choosing the potency.
Hold the comparison clearly: 30C for versatile, forgiving, repeatable work; 200C for intense acute and clear constitutional cases given less often; 1M and above for deep constitutional prescribing in single doses by experienced hands; and LMs for gentle, controllable depth in sensitive patients. Pair every potency with a deliberate repetition plan, watch for the difference between aggravation, new symptoms, and the return of old ones, and record your reasoning so each case teaches you something for the next.
Do that consistently, and potency stops feeling like guesswork and starts behaving like what it is — the final, reasoned link in the chain from case to cure.
References
- Hahnemann, S. Organon of Medicine, 6th ed. (§246–248, §269–271, §275–287).
- Kent, J.T. Lectures on Homoeopathic Philosophy.
