CBD dosage is a math problem more than a magic number. No agency has set a standard dose for over-the-counter CBD, and the FDA hasn't evaluated retail products to work out a proper one. What you can do is read milligrams carefully, start low and keep track of how you respond. Here's how to do the math for oils, gummies, vapes and flower, plus the safety limits worth knowing.
Why there's no one-size CBD dosage
Three things get in the way of a single answer. The science is thin: the FDA still lists basic open questions, such as what level of intake triggers CBD's known risks. Products differ in strength and absorption; in one review, peak levels ran higher when CBD was taken alongside a meal or in an oil-based formula. And people differ in weight, health and the medicines they take.
Two reference points put store-bought amounts in context:
- Prescription CBD. The one CBD medicine the FDA has approved is dosed by body weight for specific seizure disorders. It starts at 2.5 mg per kilogram twice a day, with liver blood tests first, and it isn't a guide for retail products.
- UK food guidance. In 2023, UK food safety regulators advised healthy adults to limit CBD from food to 10 mg a day as a precaution. They tied the advice to long-term risks such as liver or thyroid problems.
For what CBD may and may not do, read our guide to CBD's benefits.
Start low and adjust: a simple CBD dosing journal
A notebook or phone note beats guesswork. Pick one product, take a small amount and keep it steady for several days. Then adjust a single variable at a time: the amount, the time of day or whether you take it with food. Each time, log the date, the product and batch, the milligrams of CBD and any THC, whether you'd eaten, how you felt over the next few hours and any side effects.
If sleepiness, an upset stomach or appetite changes show up, scale back. The FDA notes that CBD's common side effects should improve when you stop or lower the amount. Count every source, too: CBD in a drink, a gummy and a lotion on the same day adds up.
CBD oil dosage: milligrams per ml and per dropper
Think of these steps as a do-it-yourself CBD oil dosage calculator:
- Find the total. Say the label reads 900 mg of CBD in a 30 ml bottle.
- Divide. 900 ÷ 30 = 30 mg of CBD per ml.
- Match your dropper. A full 1 ml dropper is 30 mg; a half dropper (0.5 ml) is 15 mg.
- Go smaller with drops. Drop sizes vary, but at roughly 20 drops per ml, each drop of this oil carries about 1.5 mg.
Percentage labels work the same way. A 5% oil holds about 50 mg of CBD per ml, which is why UK regulators put 10 mg at about four to five drops. If your dropper isn't marked in milliliters, use a marked oral syringe. Our cannabis tincture guide covers technique. Some oils also carry a little THC, which our full-spectrum CBD explainer covers.
CBD gummies dosage and capsules
Gummies and capsules are pre-measured. If a jar holds 750 mg across 30 gummies, each has 25 mg, and half a gummy is about 12.5 mg. Capsules list milligrams per capsule.
Swallowed CBD is slower and less predictable. In human studies, peak blood levels arrived anywhere from minutes to about four hours after a dose, and a meal can push levels higher. Wait several hours before judging a serving, and keep your timing and meals consistent while you test. If a gummy also contains THC, remember that Michigan limits adult-use edibles to 10 mg of THC a serving.
CBD vape dosage: estimating per puff
Vapes are the hardest to measure, because puff size depends on the device and on how long you draw. Say a cartridge holds 300 mg of CBD and lasts about 150 puffs: that's roughly 2 mg per puff, as a rough guide. Inhaled CBD peaks in the blood faster than swallowed CBD, so take a puff or two, give it a little time and log the count.
CBD flower: from CBD percentage to milligrams
Flower labels list cannabinoids as a percentage of weight. A gram of flower at 15% CBD holds about 150 mg of CBD, so a 0.5 g joint holds about 75 mg. Only part of that reaches your bloodstream. The one human study that measured it, according to a 2018 review, put the average absorbed share from smoking at about 31%. By that figure, the joint would deliver somewhere around 20 to 25 mg.
Taking too much CBD: side effects, liver and drug interactions
Can you overdose on CBD? It doesn't intoxicate, but more isn't harmless:
- Side effects. Sleepiness or sometimes insomnia, diarrhea, decreased appetite, and irritability or agitation.
- Liver. In studies of the prescription product, CBD raised liver enzymes in some patients. Higher doses taken with the seizure drug valproate raised that risk.
- Interactions and sedation. CBD can raise or lower the effects of other medicines, and mixing it with alcohol or other sedating drugs adds to drowsiness and the risk of injury.
- Long-term use. UK regulators say the risk of effects like liver damage or thyroid issues grows with the total amount you take over your lifetime.
The same UK guidance says CBD isn't for children, people who are pregnant, breastfeeding or trying to conceive, or anyone on medication who hasn't checked with a medical professional. Anyone on medication or with liver problems should check with a pharmacist or clinician before starting. If you take far more than you meant to and feel unwell, contact Poison Control (1-800-222-1222) or get medical care.
CBD:THC ratios and how they change the experience
A CBD:THC ratio compares milligrams. A 20:1 product has 20 mg of CBD for every 1 mg of THC, a 1:1 product has equal amounts and a 1:2 product leans toward THC. A ratio describes balance rather than strength, so two 1:1 gummies can hold very different amounts.
THC is what makes a product intoxicating, so its milligrams matter most. Many people hope extra CBD will soften THC, but a 2023 trial found no sign of that. Forty-six healthy, infrequent cannabis users inhaled 10 mg of THC with 0, 10, 20 or 30 mg of CBD. The added CBD made no measurable difference to THC's impact on memory, psychotic-type symptoms or how high people felt. Our THC dosage guide covers THC servings.
Choosing a CBD:THC ratio
| Ratio type | Examples | THC per serving | Who it suits |
|---|---|---|---|
| CBD-only or isolate | No THC listed | None | People avoiding THC entirely |
| High CBD | 20:1, 10:1 | Low | People who want minimal intoxication |
| Balanced | 2:1, 1:1 | Moderate | People comfortable with some THC |
| THC-forward | 1:2 and up | Higher | Experienced THC users |
Whatever you choose, start with the lowest THC serving, and wait until you've felt an edible's full effect before taking more. If you're drug tested, any THC matters; our CBD vs. THC comparison explains why. Keep THC products away from children and pets, and never drive after using THC.
You must be 21 or older to shop recreationally at High Society, or 18 and older with a medical card. A budtender can help you read a label in store; find the location nearest you.
