How to Dose GHB Safely: The 1mL Rule and Why Redosing Kills

GHB (G, liquid G, liquid ecstasy) causes a disproportionate number of overdoses for one specific reason: it is sold as a liquid of unknown concentration, and most people dose by volume. One milliliter of one batch might contain 500mg of GHB. One milliliter of the next batch might contain 1,500mg. Without knowing which you have, you are not dosing a drug — you are guessing at one.

This guide covers the pharmacology behind why that matters, what the “1mL rule” actually means and what it does not mean, how to measure correctly, and why redosing is the most common way people end up in an ambulance.

Quick answers

What is a safe GHB dose? There is no universal safe dose because recreational GHB has no standard concentration. A common harm reduction starting point for unknown-concentration GHB is 0.5-1mL, taken with nothing else, then waiting a full 90 minutes before deciding whether to take more.

What is the 1mL rule? A community-derived harm reduction heuristic: start with 1mL of unknown GHB. The logic is that even at the highest common concentrations (~1.5g/mL), 1mL delivers roughly 1.5g, which is near the top of the euphoric range for a non-tolerant person. It is a first-dose ceiling, not a redosing reference.

Why is redosing GHB dangerous? GHB has a short felt duration but capacity-limited metabolism. Residual drug is still in your system when you feel like it has “worn off.” A second dose stacks on top of that residual drug and can tip someone from functional into unconscious within 15-20 minutes.

How should you measure GHB? With an oral syringe, measured in 0.1mL increments. Not a shot glass, not a bottle cap, not a guess.

GHB’s dose-response curve: why the margin is so narrow

GHB is a short-acting CNS depressant with one of the steepest dose-response curves of any recreational drug. At roughly 1-2g, most non-tolerant people experience euphoria and disinhibition. At 2.5-3.5g, sedation and cognitive impairment. At 3-4g, a non-tolerant person can lose consciousness and develop life-threatening respiratory depression (PMID 26074743).

That is a roughly 2-3x safety ratio from euphoria to coma. Alcohol’s is closer to 10x. GHB leaves almost no room for error.

The pharmacokinetics make this worse. GHB is absorbed quickly, with peak plasma levels at 20-45 minutes. At low doses, the elimination half-life is approximately 30-50 minutes. But GHB metabolism is capacity-limited: at higher doses, the enzymes responsible for breaking it down become saturated, elimination slows dramatically, and the drug accumulates faster than expected (PMID 33417072). A landmark dose-escalation study in healthy volunteers found that AUC increased disproportionately with dose — meaning higher doses produce blood levels that climb far more than the dose ratio would predict — and half-life lengthened significantly as dose increased (PMID 8299669).

In plain terms: if 1g takes 45 minutes to clear, 3g does not take 135 minutes. It takes much longer. This is the pharmacological foundation of GHB overdose.

The concentration problem

GHB is synthesized as a powder or solution and sold as a liquid. There is no pharmaceutical-grade recreational supply, no standard concentration, and no labeling requirement. Concentrations in the recreational market range from roughly 0.5g/mL to 1.5g/mL or higher, depending on the source (PMID 22746383).

This means a “1mL dose” delivers anywhere from 500mg to 1,500mg or more depending on who made the batch. That 3x variation spans the full range from well below a euphoric dose to a dose capable of producing unconsciousness in a non-tolerant person.

People often “find their dose” with one batch and then apply that same volume to the next batch they acquire. This is one of the most common overdose mechanisms. The dose did not change. The concentration did.

What to do with unknown-concentration GHB:

1. Assume nothing about concentration based on previous batches, even from the same person
2. Harm reduction practice is to start with no more than 0.5mL of an unknown batch, wait 90 minutes, and assess before considering more
3. If you are confident in the source and have experience with their product, the 1mL rule is a reasonable starting point — but 0.5mL is safer

The 1mL rule: what it means and what it does not

The 1mL rule is a harm reduction heuristic, not a verified safe dose. The reasoning: at even the highest commonly encountered concentrations (~1.5g/mL), 1mL delivers approximately 1.5g of GHB — which sits at the top of the euphoric range but is unlikely to cause unconsciousness in a non-tolerant person with no other substances on board.

What the 1mL rule is: a first-dose starting ceiling for an unknown batch taken alone, by a non-tolerant person, with no other substances.

What the 1mL rule is not:

• A redosing reference
• Safe if you have any alcohol or other CNS depressants in your system
• Appropriate for tolerant users trying to feel the same effects they felt before tolerance developed
• Safe if the concentration is higher than ~1.5g/mL (which does occur)

The rule exists because it is more likely to prevent you from accidentally taking 3g than no rule at all. It is a floor, not a guarantee.

Redosing: why the second dose is the dangerous one

GHB’s effects are felt for roughly 2-4 hours. When the euphoria fades, the instinct to redose is strong and completely predictable. This is where most serious overdoses happen.

The problem: the felt duration of GHB does not track its blood level. When the pleasant effects have mostly worn off, a meaningful amount of drug is still present in your system. The capacity-limited metabolism means clearance is slower than you perceive. Your body is still processing the first dose when you take the second.

What happens when you redose too soon: the second dose stacks onto residual drug, immediately saturating the metabolic enzymes that are still working on the first dose. Elimination slows further. Blood levels climb faster than expected. The person goes from “feeling fine” to unconscious in 15-20 minutes.

Minimum time between GHB doses: 3-4 hours from the time you took the first dose, not from when you stopped feeling it. That distinction matters because GHB’s subjective duration runs ahead of its actual clearance.

Reduce the redose amount. Harm reduction guidelines suggest that if 1mL was taken first, any redose should be less — 0.5-0.75mL — not the same amount. The second dose arrives in a system that is not fully cleared.

The gap-drinking trap

At raves and festivals, the 2-4 hour felt duration of GHB leaves a gap that people frequently fill with alcohol. This is one of the most dangerous patterns in recreational GHB use. Alcohol consumed during the gap is still active when the next GHB dose hits, creating a combined CNS depressant load that neither substance alone would produce at those quantities.

The full mechanism and clinical data are covered in detail in the GHB and alcohol post. The short version: do not drink in the gap between doses, and do not use GHB if you have been drinking.

How to measure GHB

The single most practical harm reduction step for GHB dosing is using the right tool to measure it.

Use an oral syringe. Oral syringes are the only practical way to measure GHB in 0.1mL increments. A 1mL or 5mL oral syringe lets you dose 0.5mL, 0.75mL, or 1.0mL accurately. Shot glasses, bottle caps, and spoons do not.

Oral syringes on Amazon — 1mL and 5mL sizes, available in multi-packs for a few dollars. This is one of the most cost-effective harm reduction tools for GHB specifically.

A few rules for syringe use:

• Do not share syringes across different batches. If your friend has a different batch and you “borrow” their syringe with their residual fluid, you may ingest an unknown dose.
• Label your syringe if you are at a multi-day event and may forget which batch it belongs to.
• Rinse and dry between uses if reusing over a session.

GHB tolerance and why it changes everything

Regular GHB use — daily or near-daily — builds tolerance rapidly and significantly. Tolerant users may take doses 3-5x higher than what would cause coma in a non-tolerant person. This compresses the safety margin further and removes the cushion the 1mL rule provides.

Tolerance also creates a serious secondary risk: GHB dependence and withdrawal. Unlike most recreational drugs, GHB withdrawal after heavy daily use can cause seizures, delirium, and death. Do not stop abruptly after a period of daily use. If you are physically dependent on GHB, a medically supervised taper or inpatient detox is the appropriate path.

If someone overdoses

GHB overdose presents as sudden loss of consciousness, inability to be roused, vomiting while unconscious, and slow or labored breathing. The transition from conscious to unresponsive can happen in minutes. For a full clinical description, see the GHB and alcohol guide, which covers overdose response in detail.

The immediate steps:

1. Call emergency services. Do not wait to see if they wake up.
2. Recovery position. On their side, one arm under their head, so they cannot aspirate vomit.
3. Do not leave them alone. Breathing can stop.
4. Tell paramedics what was taken, including any alcohol or other drugs.

The bottom line

GHB’s overdose risk is not primarily about dose size — it is about not knowing what you are dosing, not measuring it properly, and redosing before the first dose has cleared. The 1mL rule addresses the first problem only, and only partially. Oral syringes address the second. Waiting a minimum of 3-4 hours between doses addresses the third.

None of these steps eliminate the risk. GHB has a narrow enough therapeutic window that even careful use carries meaningful risk, especially when combined with alcohol or other CNS depressants.

For a broader overview of GHB effects and risks, see the GHB harm reduction guide. For dangerous combinations beyond alcohol, see the interaction checker. For general harm reduction, visit the FAQ.

Sources: PMID 26074743 | PMID 33417072 | PMID 8299669 | PMID 22746383