At first glance, the bitter Twitter battle against CVS over birth control pills this week may have convinced you that the pharmacy giant was blocking access to the contraceptive. But like most Twitter scuffles, it's complicated.

Here's what's really happening.

CVS Caremark, a CVS subsidiary that works with pharmaceutical companies to set prescription pricing for customers of CVS and other pharmacies, has reduced how much it'll reimburse retailers that only sell one product. One such online startup, Pill Club, mails women birth control in packages filled with other goodies like stickers that say "You are magical" and chocolate. CVS' move means Pill Club will be reimbursed at a lower rate for customers whose insurance is tied to CVS Caremark, making it so the company can no longer afford to service those people.

"Pill Club members with pharmacy coverage through CVS Caremark are at risk of their birth control access being disrupted," Pill Club said in a statement on their website.

As a result, the hashtags #CVSDeniesCare and #BoycottCVS started trending on Thursday, with Pill Club itself retweeting posts with the hashtag, including one from NARAL Pro-Choice America president Ilyse Hogue, which lambasted CVS for reducing women's access to birth control.

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While Pill Club says tens of thousands of women have pharmacy coverage through CVS Caremark, it's unclear how many current Pill Club customers will be affected. If you have health insurance through your employer, your company might decide to use CVS Caremark to manage your prescription benefits. It could also contract a health insurance company that has hired CVS Caremark to manage pharmacy coverage. You don't have much choice in the matter.

Basically, if you use Pill Club and your insurance is tied to CVS Caremark, you may have to find a new way to get birth control if CVS doesn't reverse its decision.

While this doesn't mean CVS istaking away your general access to birth control, CVS critics believe people should be able to buy their birth control wherever they choose, whether online or in-person. CVS' decision makes this harder for some consumers who have chosen Pill Club to get their birth control.

This scuffle highlights that a new wave of online health startups providing prescription drugs are still very much tied to larger, more established corporations that deal directly with drug companies to set pricing and reimbursement rates.

Other online pharmacies have agreed to CVS' rates. Joel Wishkovsky, CEO of Simple Health, which also provides birth control delivery, told Mashable in a statement that it will continue serving CVS Caremark customers.

“We want to assure our patients that they are not at risk of losing their birth control coverage through Simple Health. We have our patients’ back -- regardless of whether their insurance uses CVS Caremark. The dispute surrounding CVS Caremark is about profits for mail-order providers and not actually about access to healthcare," he said. "We are against using patients as bargaining chips in negotiations and we have not and will not turn away CVS Caremark patients.”

In an email to Mashable, a CVS spokesperson explained that, "Our coverage of contraceptives is widespread throughout our network of 68,000 pharmacies, ensuring accessible and affordable access to our members. The accusations being made by Pill Club against CVS Caremark are extremely misleading. Pill Club continues to be a participating pharmacy in our network and there is no impact on its customers’ access to contraceptives. We are committed to providing access to women’s health care and it is irresponsible for Pill Club to suggest otherwise in an effort to maximize their profits at the expense of our PBM clients."

On its website, Pill Club stated, "We believe that CVS simply doesn’t understand how devastating these cuts will be to Pill Club and the women we serve. We believe they are trying to save money without knowing all of the consequences. We hope CVS will change course."

People shared personal stories and promises to leave CVS after learning of the change. One person even announced she had already moved all of her prescriptions from CVS.

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Mashable has reached out to other prescription delivery start-ups to see how CVS' decision may affect them.

UPDATE: Aug. 16, 2019, 4:07 p.m. EDT This post has been updated to include a statement from Simple Health, which already complies with CVS Caremark's reduced reimbursement rate.