Can I Take 2 Zyrtec? What the Box Says and Who Gets More

Not on your own. Zyrtec's Drug Facts label says "do not take more than one 10 mg tablet in 24 hours." Doctors sometimes prescribe more for chronic hives, but that is a plan they set and watch. If you already took a second one by mistake, call Poison Control at 1-800-222-1222. In Canada, call 1-844-764-7669, or 1-800-463-5060 in Quebec (Health Canada).

That last line comes straight from the box: "In case of overdose, get medical help or contact a Poison Control Center right away."

This article provides general information about medication management and is not a substitute for professional medical advice. Consult your doctor or pharmacist for advice specific to your medications.

Can I Take 2 Zyrtec in One Day?

The box answer is no. One 10 mg tablet covers 24 hours. Two tablets in one day is 20 mg, double what the box allows.

There is also a reason the limit sits at one. In the trials behind the original prescription label, people 12 and older took 5 to 20 mg a day for allergies or chronic hives. The label's summary: "In general, the 10-mg dose was more effective than the 5-mg dose and the 20-mg dose gave no added effect."

Drowsiness, on the other hand, did climb with the dose. The same label reports it in about 6 in 100 people on placebo, 11 in 100 on 5 mg, and 14 in 100 on 10 mg.

Some people still ask about splitting it: "can I take 2 Zyrtec 12 hours apart?" Spacing them out does not change the math. Two 10 mg tablets 12 hours apart are still 20 mg inside 24 hours. When one tablet is not enough, that is the moment to call your doctor, not to add a second one.

Accidentally Took 2 Zyrtec: What to Do

It happens: you take your morning tablet, forget, and take another.

1. Call Poison Control: 1-800-222-1222. The box tells you to "get medical help or contact a Poison Control Center right away" in case of overdose. Tell them how much you took, when, and what else you take.
2. Watch for sleepiness. The 2004 label describes an adult who took 150 mg and was "somnolent but did not display any other clinical signs." That is one case report, not a safety margin.
3. Do not drive until you know how you feel. The box says to "be careful when driving a motor vehicle or operating machinery," and that is at the normal dose. It also says to "avoid alcoholic drinks" and warns that "alcohol, sedatives, and tranquilizers may increase drowsiness."
4. Before your next tablet, check with Poison Control or your pharmacist on timing.

The UK's NHS is calmer about it: "Taking an extra dose is unlikely to harm you or your child." But it still says to get urgent advice if "your child takes more than the recommended dose of cetirizine, even if they have no symptoms," or if you are worried or have "symptoms such as a headache, feeling sleepy or a fast heartbeat." In the US, Poison Control is the number for that call.

For other medicines, see our guide to taking medication twice by mistake. If the double dose was another allergy medicine, see a double dose of montelukast.

Can You Take Zyrtec Twice a Day for Hives?

This is where "more than one" really happens, and only with a doctor. Guidelines for chronic hives, meaning hives that last more than 6 weeks, let doctors raise the dose of antihistamines like Zyrtec. A 2022 review on managing hives in primary care, which uses that 6-week line, says these antihistamines "should be used at up to four times standard dose in those patients with insufficient response to standard dose, although this remains off‐licence." Off-licence means outside the approved label.

How strong is the evidence? The 2022 review calls the step "supported by substantial evidence." A 2021 systematic review was less sure: it found only 14 usable studies, just 2 of them on cetirizine, and said the up-dosing advice is "based mainly on expert opinion." The most frequent side effects in those studies were headache and drowsiness. A small Japanese study gave 20 mg to 9 people whose hives did not clear on 10 mg, and found that "Doubling the dose of cetirizine may be efficacious." That is 9 people, not blinded.

So if you have hives, read the Zyrtec Hives box first. It carries the same one-tablet limit. It tells you to stop and ask a doctor if "symptoms do not improve after 3 days of treatment" or "the hives have lasted more than 6 weeks," and to "see your doctor for a medical exam" if you do not know the cause of your hives. A doctor may look at other options, including a higher prescribed dose.

Zyrtec Dose for Elderly and Kidney Disease

Here the limit can be lower than one tablet, and the boxes do not all say the same thing.

Sources: Zyrtec Allergy, Children's Zyrtec chewables, Children's Zyrtec liquid, and Zyrtec-D Drug Facts labels.

The two Children's products above print a 5 mg daily limit for adults 65 and older. Zyrtec Allergy and Zyrtec-D send that age group to a doctor instead, even though each Zyrtec-D tablet holds 5 mg of cetirizine. So for adults 65 and older, these four boxes give either a 5 mg cap or "ask a doctor."

The reason is how the body clears it. The 2004 label says cetirizine "is known to be substantially excreted by the kidney." In its studies:

• People with an average age of 77 had a 50% longer half-life than adults averaging 53.
• People with moderate kidney disease had about 3 times the half-life and 70% lower clearance.
• People with chronic liver disease had a 50% longer half-life.

That label recommended a lower dose for moderate kidney disease, dialysis, and liver disease. Today's box puts it simply: "Ask a doctor before use if you have liver or kidney disease. Your doctor should determine if you need a different dose."

If you help a parent with their allergy medicine, this table is worth a screenshot. Summer brings its own antihistamine question: see allergy meds in hot weather.

Can You Take Zyrtec and Zyrtec-D Together?

This is an easy way to take "2 Zyrtec" without noticing. Zyrtec-D has 5 mg of cetirizine in every tablet, plus the decongestant pseudoephedrine. Its box says to "take 1 tablet every 12 hours; do not take more than 2 tablets in 24 hours." Two tablets hold 10 mg of cetirizine already. Add a plain Zyrtec and you are at 20 mg, more cetirizine than either box allows on its own. The Zyrtec-D box also says not to use it with a prescription MAOI ("certain drugs for depression, psychiatric, or emotional conditions, or Parkinson's disease") "or for 2 weeks after stopping the MAOI drug." If a stuffy nose has you reaching for both, ask your pharmacist which one fits. For when to take Zyrtec-D in your day, see the best time to take Zyrtec.

Hydroxyzine is a cousin worth knowing about. The 2004 label calls cetirizine "a human metabolite of hydroxyzine," which means your body makes cetirizine when it breaks down hydroxyzine. The Zyrtec box tells you not to use it if you have ever had an allergic reaction "to this product or any of its ingredients or to an antihistamine containing hydroxyzine." If you take prescription hydroxyzine, ask the prescriber before adding Zyrtec. Our guide to taking 2 hydroxyzine 25 mg covers that drug's own limits.

Decongestants have their own problem for blood pressure; see cold medicine and high blood pressure. Combination cold medicines deserve the same box check; see how we read the DayQuil and NyQuil boxes.

Taking 2 Zyrtec for an Allergic Reaction?

Stop and check what kind of reaction it is. If there is trouble breathing, swelling of the lips, tongue or throat, or fainting, do not wait to see whether Zyrtec works. MedlinePlus says: "If someone is having a serious allergic reaction, call 911. If an auto-injector is available, give the person the injection right away." The Zyrtec Hives box agrees: "Get emergency help immediately" if hives come with signs like these, and "never use this product as a substitute for the epinephrine injector." If the reaction is to Zyrtec itself, the Zyrtec box says to "Stop use and ask a doctor" and "Seek medical help right away."

For hives or itching that will not settle on one tablet, the problem may not be the dose at all. The Zyrtec Hives box makes two points worth reading twice:

• Do not use it to prevent hives from a known cause such as foods, insect stings, medicines, or latex, because it "will not stop hives from occurring." Avoiding the cause "is the only way to prevent them."
• Hives "that are an unusual color, look bruised or blistered" or "that do not itch" need a doctor before you use it.

A second tablet does not address either of those.

How Pillo Helps

If you have ever stood at the counter asking "Did I already take it?", a dose record answers it. Pillo's persistent alarm keeps ringing until you respond, and marking the dose as taken leaves a record, so your dose history shows when you took it. Dose spacing alerts flag it if you schedule two doses of a medicine too close together.

Caring for an older parent? Pillo's dependents feature lets you manage their medicines on your own phone. It is free for up to two dependents; a third needs the paid plan.

Download Pillo on Google Play

FAQ

Is 20 mg of Zyrtec too much?

For most adults, it is twice the box limit of one 10 mg tablet in 24 hours. In the trials behind the original prescription label, 20 mg "gave no added effect" over 10 mg. Doctors sometimes prescribe 20 mg or more for chronic hives, but only as a supervised plan.

Can I take Zyrtec and Benadryl or Claritin together?

That is a call for your doctor or pharmacist. Each box sets its own daily limit, and Zyrtec's box says to "Ask a doctor or pharmacist before use if you are taking tranquilizers or sedatives." If you took diphenhydramine (Benadryl) by mistake at the wrong time, see our guide to diphenhydramine taken in the morning.

My child took an extra Zyrtec. What should I do?

Call Poison Control at 1-800-222-1222, even if your child seems fine. The box says to "get medical help or contact a Poison Control Center right away" in case of overdose. The UK's NHS also says to get urgent advice for a child who took more than the recommended dose, "even if they have no symptoms."

How many Zyrtec can I take for hives?

The Zyrtec Hives box sets the same limit as the allergy box: "do not take more than one 10 mg tablet in 24 hours." Higher doses for chronic hives are prescribed by a doctor who follows up. The same box says to stop and ask a doctor if hives do not improve after 3 days or last more than 6 weeks.

I'm pregnant and took 2 Zyrtec. What should I do?

Let your prenatal care provider know, and call Poison Control at 1-800-222-1222. The box already says "if pregnant: ask a health professional before use," even for one tablet. For breastfeeding, the same box says "not recommended."

What if I took 2 Zyrtec and feel very sleepy?

Do not drive, avoid alcohol, and call Poison Control at 1-800-222-1222. Tell them about any sedatives or sleep medicines you take. The box asks you to be careful with driving even at one tablet. If you feel very unwell, remember the box's overdose line: "get medical help" right away.

This article is for informational purposes only and does not constitute medical advice.