A common misconception about the Medicaid program is that all poor people automatically qualify for the health insurance program. They don't — and depending on where you live, it can be incredibly hard to get coverage.

There's a big divide between the states that participated in Obamacare's Medicaid expansion and those that didn't. States that signed up extended Medicaid eligibility to all adults earning up to 138 percent of the federal poverty level, or about $16,105 for an individual.

But if you live in one of the 23 states that didn't expand coverage, the limits can be really strict, according to a new report from the Kaiser Family Foundation. The result is that a lot of people end up being caught in a gap where they make too much money to qualify for Medicaid but too little to get assistance through the new Obamacare health insurance exchanges.

As the Kaiser foundation reports, 14 states currently set Medicaid eligibility for parents at below half of the federal poverty level. One of the most stringent requirements is found in Texas, the largest state sitting out the Medicaid expansion. Medicaid coverage in Texas is cut off for parents earning above 19 percent of the federal poverty level — or $3,760 for a family of three. The eligibility cutoff for parents of a dependent child, according to the Kaiser foundation report, is only lower in Alabama ($3,562), and it isn't much higher in Missouri ($4,551) or Louisiana ($4,479). The income thresholds do increase with more dependent children.

With the exception of Wisconsin, none of the non-expansion states provide full Medicaid coverage for childless adults. As you can see below, it's not hard in a lot of states to wind up making too much money to qualify for Medicaid.

These charts are a pretty strong illustration of what's known as the "coverage gap" in states that opted not to expand Medicaid, which the Supreme Court allowed them to do in a 2012 ruling. According to Kaiser estimates, there are nearly four million people who earn too much to qualify for Medicaid in these 23 states, but they also earn less than the federal poverty level, which is the minimum income requirement to qualify for premium subsidies on ACA's health insurance exchanges.

That coverage gap could potentially shrink this year as more Republican governors pursue alternative ways to cover their low-income populations with enhanced Medicaid expansion funding provided by the ACA. With state legislatures starting to return, we'll soon see if Republican lawmakers in those states are more willing to accept this huge part of the ACA.

UPDATE: An earlier version of this post incorrectly stated that Medicaid eligibility for Texas parents was cut off at 14 percent of the federal poverty level because of an error in an advanced copy of the report provided by the Kaiser foundation.