GHB Dosing: Start at 0.5mL, and Why Redosing Kills

Start an unknown batch at 0.5mL, take nothing else with it, and wait 3 to 4 hours before deciding anything. GHB sends people to hospital out of proportion to how much of it gets used, and the reason is simple: it is sold as a liquid of unverified concentration and almost everyone doses by volume. One millilitre of one batch might hold 500mg. One millilitre of the next might hold 1,500mg. You are not dosing a drug, you are guessing at one.

There is no clinical trial range to fall back on here, unlike MDMA. Everything below is harm reduction consensus reasoning from pharmacology, and the pharmacology is the part worth understanding, because it explains why the mistakes people make with GHB are the specific mistakes they make.

Two grams from euphoria to coma

GHB has one of the steepest dose-response curves of any recreational drug. For a non-tolerant person: roughly 1 to 2g gives euphoria and disinhibition, 2.5 to 3.5g gives sedation and cognitive impairment, and 3 to 4g can mean unconsciousness and life-threatening respiratory depression.

That is a 2 to 3x ratio from the effect you want to the one that stops your breathing. Alcohol’s equivalent ratio is closer to 10x.

The kinetics make it worse. GHB peaks in plasma at 20 to 45 minutes, and at low doses the elimination half-life runs about 30 to 50 minutes. But its metabolism is capacity-limited: the enzymes that break it down saturate, so at higher doses clearance slows sharply and drug accumulates faster than the dose increase predicts. A dose-escalation study in healthy volunteers found the area under the curve rose disproportionately with dose, and half-life lengthened significantly as dose went up.

Put plainly: if 1g clears in 45 minutes, 3g does not clear in 135. It takes considerably longer. That single fact is the foundation under every GHB overdose.

You are dosing a volume, not a drug

There is no pharmaceutical-grade recreational GHB, no standard concentration, and nothing resembling a label. Analyses of recreational-market samples put concentrations anywhere from roughly 0.5g/mL to 1.5g/mL or higher.

So “1mL” means 500mg from one bottle and 1,500mg from another. That threefold spread covers the entire distance from a dose you barely notice to a dose that puts a non-tolerant person on the floor.

The common overdose story is not someone taking a wild amount. It’s someone who found their dose with one batch and carried the same volume over to the next one, often from the same dealer. The dose didn’t change. The concentration did.

Assume nothing about a new batch, even from a familiar source. Start at 0.5mL, wait 3 to 4 hours, then assess.

What the 1mL rule is actually for

The 1mL rule is a community heuristic with no trial behind it. The reasoning: even at the strongest concentrations commonly encountered, around 1.5g/mL, one millilitre delivers about 1.5g, which sits at the top of the euphoric range and is unlikely to knock out a non-tolerant person who has taken nothing else.

Read it as a first-dose ceiling, not a target. It assumes a concentration you cannot verify. Halving it to 0.5mL costs you almost nothing and leaves real headroom if the batch turns out stronger than you assumed, which is exactly the scenario the rule exists to survive.

It is also not a redosing reference, not safe with any alcohol or other depressant on board, not appropriate for a tolerant user chasing an old effect, and not safe at all if the concentration runs above 1.5g/mL, which does happen. The rule is worth more than no rule. That is the whole of its value.

The second dose is the dangerous one

GHB feels like it lasts 2 to 4 hours. When the euphoria fades, wanting more is predictable rather than reckless, and this is where most serious overdoses happen.

The felt duration does not track the blood level. When the pleasant part has mostly gone, a meaningful amount of drug is still in you, and capacity-limited metabolism means it is clearing more slowly than your experience suggests. A second dose lands on top of that residual drug and immediately saturates enzymes that are still working on the first one. Elimination slows further, blood levels climb faster than the arithmetic implies, and someone goes from talking normally to unrousable inside 15 to 20 minutes.

Minimum 3 to 4 hours between doses, timed from when you took the first one, not from when you stopped feeling it. That distinction is the whole rule.

And make any redose smaller. If the first was 1mL, a second should be roughly 0.5 to 0.75mL, because it is arriving in a system that has not finished with the first.

Don’t drink in the gap

The 2 to 4 hour felt duration leaves a gap that people fill with alcohol, and at raves that pattern is close to universal. The alcohol is still active when the next GHB dose lands, producing a combined depressant load neither substance would produce alone at those quantities.

The mechanism and the clinical data are in the GHB and alcohol post. The short version: no drinking in the gap, and no GHB if you have been drinking.

Measure it with a syringe

The most useful practical step in GHB harm reduction is owning the right tool. An oral syringe, 1mL or 5mL, is the only realistic way to measure in 0.1mL increments, which is what dosing 0.5mL versus 0.75mL actually requires. Pharmacies sell them for dosing children’s medicine. Shot glasses, bottle caps and spoons cannot do this.

Three rules once you have one:

• Never use someone else’s syringe. Residual fluid from a different batch is an unknown dose sitting in the barrel.
• Label it at a multi-day event, when remembering which batch it belongs to gets harder than you expect.
• Rinse and dry it between uses across a session.

Tolerance removes the cushion

Daily or near-daily use builds tolerance fast. Tolerant users may take three to five times what would put a non-tolerant person into a coma, which compresses the margin further and empties the 1mL rule of whatever protection it had.

Tolerance brings something worse with it. GHB withdrawal after heavy daily use can cause seizures, delirium and death, which is not true of most recreational drugs. Do not stop abruptly after a period of daily use. Physical dependence on GHB needs a medically supervised taper or inpatient detox, and that is a genuine medical situation rather than a matter of willpower.

If someone goes under

GHB overdose looks like sudden loss of consciousness, no response to being shaken or shouted at, vomiting while unconscious, and slow or laboured breathing. The move from conscious to unresponsive can take minutes.

1. Call emergency services. Do not wait to see whether they wake up.
2. Recovery position. On their side, one arm under the head, so they cannot aspirate vomit.
3. Stay with them. Breathing can stop.
4. Tell paramedics everything that was taken, alcohol included. It changes what they do.

The overdose risk here is not really about taking too much. It’s about not knowing what you’re dosing, not measuring it properly, and redosing before the first dose has cleared. A syringe fixes the second problem. Starting at 0.5mL blunts the first. The 3 to 4 hour minimum handles the third.

None of it makes GHB safe. The window between the effect people want and respiratory depression is narrow enough that careful use still carries real risk, and any depressant in the mix narrows it further.

For the broader picture see the GHB guide, and check the interaction checker before combining anything.

Sources

PMID 8299669 | PMID 26074743 | PMID 33417072 | PMID 22746383