Your guide to the 28-day prescription rule for controlled substances

Key takeaways

• The 28-day rule is an informal term referring to the waiting period between refills for controlled substance prescriptions, influenced by federal and state laws, and insurance policies.
• Insurance companies regulate refill timelines, often using percentage-based allowances, such as requiring that 75% of a non-controlled substance prescription be used before a refill is approved, while controlled substances may require 85%.
• Federal and state laws impose restrictions on refills, with certain substances not allowing refills, and others limited to five refills within six months of the prescription date.

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Overview

Federal law in the United States regulates most drugs and divides them into five groups, which are known as Schedule I, II, III, IV, or V.

Medications are grouped into these schedules according to their medical value, their potential to cause harm, and the likelihood of misuse. Medications in these groups are known as controlled substances.

Schedule I drugs have no medical use, according to the law. Medications in Schedules II through V may be used for medical purposes and need to be prescribed by a doctor. Of these, Schedule II drugs have the highest potential for harm and misuse, while Schedule V drugs have the lowest. 

If you have a medical prescription for a controlled substance, you might not be able to refill your prescription early. This is what’s informally known as the 28-day rule for controlled substances. 

The 28-day prescription rule for refills

The 28-day rule is not a formal regulation. It refers to the number of days you may need to wait between refills of 30-day prescriptions that are considered controlled substances.

If you have a medication that follows the 28-day rule on a 30-day supply, it means you can get a refill no earlier than 2 days before the 30 days are up. The number of days between refills varies significantly, though, so this is not a set-in-stone “rule.”

Federal law, state law, and insurance companies have their own regulations that might apply to your specific prescription.

In general, however, the waiting period for refills is longer for controlled substances to reduce the chance of misuse. Misuse refers to taking a drug in a way that differs from how it is prescribed.

Insurance companies

Insurers set their own rules about when they cover the cost of a prescription refill. If you refill a medication early, your pharmacy might give you the drug, but your insurance might not cover the cost. Some insurers call this a “refill too soon” denial.

Insurance company refill regulations can also go by percentages. In this case, you have to use up a certain percentage of your prescription before you can get a refill.

Often, an insurance company may have a 75% refill allowance for all prescriptions, except for controlled substances and stimulants. These may have an 85% allowance.

This means the insurance company won’t approve your refill until you have only 15% of your medication left. They use the dates from when you last filled the prescription to calculate how much is left.

Let’s say you picked up a 30-day supply of a non-controlled, non-stimulant substance on January 1. First, the company will determine what 75% of 30 days is. In this case, it’s 22.5 days. So, you could pick up a refill starting on January 23.

If the medication is a controlled substance, you have to wait until you have used 85% of the supply. Because 85% of 30 days is 25.5 days, you can get a refill starting on January 26.

State law

Even though your insurance company might pay for a refill, state law might forbid a refill or set a different timeline for refills. In California, for example, the refill rules for controlled substances are:

• A person cannot get refills on Schedule II substances.
• No prescriptions for Schedule III or IV substances can be refilled more than five times or for a total that exceeds a 120-day supply. 

So, if you have a prescription for a Schedule III substance that is for a 7-day supply, you can refill it five times. Your total refills is a 35-day supply. You cannot refill the prescription a sixth time, even if the doctor wrote that allowance in the prescription.

Federal law

Federal law also has rules around refills for controlled substances. 

For Schedule II substances, there are no refills on prescriptions. But a physician can write multiple prescriptions for the Schedule II drug as long as all of the prescriptions together do not exceed a 90-day supply. On each prescription, the doctor must write the earliest date that it may be filled.

There is a maximum of five refills for Schedule III and IV substances, and each refill can be no later than 6 months after the date of the prescription. 

What are the new rules from the DEA?

The United States Drug Enforcement Administration (DEA) announced new regulations for prescribing controlled substances in 2025. These rules are related to telemedicine prescribing of controlled substances.

The DEA has introduced a special registration system for telemedicine providers, where providers can register for different programs depending on whether they will dispense controlled substances:

• Special Registrations is for anyone prescribing Schedule III to V substances
• Advanced Special Registration is for specialized providers prescribing Schedule II to V substances

This means that people will be able to access controlled substances without making an in-person appointment, as long as the provider is legally registered.

The DEA also proposed a rule allowing greater flexibility in prescribing buprenorphine (Belbuca), a medication used to manage opioid use disorder (OUD), via telemedicine.

These proposed rules will help to expand access to essential medications for many people.

Examples of controlled substances per schedule

These are examples of some of the prescription medications that are on the controlled substance lists and may have limitations when it comes to refills:

Schedule II

• hydromorphone (Dilaudid)
• hydrocodone (Hysingla)
• methylphenidate (Concerta, Ritalin)
• amphetamine/dextroamphetamine (Adderall)
• morphine CS (MS Contin)
• oxycodone (OxyContin, Percocet)

Schedule III

• buprenorphine (Belbuca)
• testosterone enanthate (Xyosted)

Schedule IV

• alprazolam (Xanax)
• diazepam (Valium)
• tramadol (Ultram)
• eszopiclone (Lunesta)

Schedule V

• codeine preparations (Robitussin A-C, Pediacof)
• lacosamide (Vimpat)
• pregabalin (Lyrica)

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What is an emergency refill?

An emergency refill is when a pharmacist gives you a short-term supply of your medication when you haven’t had a chance to get a new prescription. 

The laws around emergency refills vary by state and depend on whether your medication is a controlled substance.

Each state has a day supply allowance as well as a frequency limit. For example, your state might allow a 72-hour supply of a non-controlled substance, one time only. You must get a new prescription to have a longer supply and you can get only one emergency refill.

Most states do not allow for emergency refills of controlled substances. Others might allow for refills on Schedule III, IV, or V medications only. 

According to federal law, a pharmacist may give an emergency refill of a Schedule II substance only upon getting oral authorization from a licensed prescribing practitioner.

What is a quantity limit exception?

Some insurance companies place a limit on the number of units (tablets, vials, etc.) of a drug that you can receive in a period of time.

If a doctor prescribes more than the limit, your insurance company may not provide coverage for the additional units, unless you get a quantity limit exception.

A request for a quantity limit exception must be completed by a doctor, and it needs approval from the regulating entities in your county or state.

Summary

Insurance companies, state law, and federal law have regulations about prescription refills. The 28-day prescription rule refers to how long you have to wait to refill a medication that is on the list of controlled substances. It is not a formal rule but guides many regulations.

In general, you have to wait longer for a controlled substance refill than for a non-controlled substance.

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