90-days vs. 30-days supply: it makes a difference in adherence

More evidence that 90-days supply improves drug adherence over 30-days

March 27, 2018

Chronic conditions make up more than 80 percent of the U.S. health care spend.2 Studies show that 50 percent of people don’t take their medicines as prescribed.3 Improving adherence can reduce complications and hospitalization rates for many chronic conditions.4

Previous studies comparing 90-days and 30-days supply looked at groups with restricted benefit plans; members were steered toward use of 90-days supply. We wanted to see if the adherence correlation held up with a benefit design that gave members more options. We also wanted to see if the 90-day advantage could hold up over a longer period.

The benefit design options included:

  • Keeping the 30-days supply option available (not just one or two grace fills before a penalty)
  • Keeping the 90-days supply option open to:
  • Delivery by mail service or
  • Pick-up at local pharmacy

Then, we followed the members for more than 18 months. That amount of time would take us through a doctor’s prescription reauthorization cycle.

This study looked at three chronic medication classes: diabetes, high blood pressure and high cholesterol.

What did we learn?

Members filling their cholesterol lowering, high blood pressure and diabetes medications with 90-days supplies had an associated significantly higher adherence at 270-days follow up. This higher adherence rate persisted at 540-days follow up; this suggests the gain in adherence is stable over time.


The analysis used claims data from nearly 1.3 million commercially insured members who were continuously enrolled throughout 2007 and did not have a mandatory mail requirement. These members were available for the 270-days follow up analysis. The 540-days follow up included 905,736 members.

Members had a claim for a chronic prescription for a cholesterol-lowering drug, a high blood pressure drug, or an oral diabetes drug. Adherence was measured using proportion of days covered (PDC).


At 270 days, adherence was 6 to 10 percentage points higher for the 90-days supply group compared to the 30-days supply group. At 540 days, adherence was even better. It was 7 to 10 percentage points higher for the 90-days supply group compared to the 30-days supply group. Members who received their medications in 90-days supplies rather than 30-days supply were 40 percent less likely to have adherence problems. This means they continued to follow their doctor’s prescribed drug regimen.

There was no difference in adherence rates between the members that got their 90-days supply from the retail store or by mail. The 90-days supply was the key, not the delivery method.


This study suggests that 90-days supply can improve adherence from 7 to 10 percent for conditions like high cholesterol, high blood pressure and diabetes. Improved adherence can result in improved health outcomes. Further study is needed to quantify impact.

What does this mean for you?

The added convenience, as well as member cost savings often associated with 90-days supply, are likely key factors in the improved adherence. Results suggest that plan sponsors looking to increase adherence should look at 90-days supply as a key strategy. If it is not already in the benefit plan, add it. If it is already there, plan sponsors can work with Prime to further promote the option, through incentives or education.

In addition, adherence programs through GuidedHealth® can monitor and reach out to members with chronic conditions to help keep them on prescribed therapy plans.


  1. Hermes M, et al. Adherence to Chronic Medication Therapy associated with 90-Day Supplies Compared with 30-Days Supplies. J Manag Care Pharm 2010; 16:141-142.
  2. “Gerteis J, Izrael D, Deitz D, LeRoy L, Ricciardi R, Miller T, Basu J. Multiple Chronic Conditions Chartbook. [PDF – 10.62 MB] AHRQ Publications No, Q14-0038. Rockville, MD: Agency for Healthcare Research and Quality; 2014. Accessed at: https://www.cdc.gov/chronicdisease/overview/index.htm
  3. “Medication adherence: Who cares?” Mayo Clin Proc. 2011 April; 86(4): 304–314. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3068890/
  4. Sokol MC, etal. Impact of medication adherence on hospitalization risk and health care costs. Med Care 2005;43:521-30.

GuidedHealth is a registered trademark of Prime Therapeutics LLC.

Adherence to Chronic Medication Therapy Associated with 90-day Supplies Compared to 30-day Supplies (Spring 2010)

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