Does an insurer lull its insured into a sense of complacency sufficient to prevent the insured from filing suit when it advises her three months before prescription runs that it is reconsidering its previous demal of her claim? Louisiana Health Service and Indemmty Company d/b/a Blue Cross and Blue Shield of Louisiana (defendant) is appealing the trial court’s affirmative answer to this question.

Defendant issued a major medical insurance policy to Loretta Webb (plaintiff), effective July 1,1992. She was hospitalized October 31 through November 2,1992, with chest pain. Thomas Hall, plaintiff’s attending physician, indicated in plaintiffs medical records that plaintiff had a two-year Mstory of chest pain. Timely submitted claims by plaintiffs health-care providers were consequently de-med under the preexisting-condition exclusion in defendant’s policy.

In January 1993, plaintiff wrote defendant, asking it to reconsider her claim and enclosing a letter from Hall. Plaintiff demed she gave Hall a history of preexisting chest pain. In June 1993, defendant sent a letter to Hall explaining the basis for demal of the claim. The letter concluded, “I do not believe that our office has made an error. However, if there is medical information that we do not have that would be offered to change our position, we would be happy to review same.” On November 10,1993, Hall wrote defendant stating his record “must be erroneous”; he asked defendant to take the correction into account and reconsider its demal of the claim. On November 15, 1993, defendant wrote Hall acknowledging receipt of Ms letter and statmg, “As soon as our medical staff has completed their review, you will be notified of their decision.” A copy of tMs letter was sent to plaintiff.

The record does not mdicate when, if ever, defendant notified plaintiff it had deMed her claim a second time. Dawn Clayton, defendant’s manager, testified the claim was re-reviewed and re-deMed in November 1993. Plamtiff testified she concluded m June 1993 that defendant defmitely was not gomg to honor her claim. That was when she retained counsel. She further testified, however, that it was her “impression that if the medical records were cleared up by Dr. Hall, that Blue Cross would pay the claim.” She did not explam how she got that impression. She stated, “If Dr. Hall corrected that entry, that seemed to be what the main problem was, which was an erroneous entry to begin with. Yes, if he cleared [it] up, I didn’t see what the ^problem was with the policy ... and it being paid.” Plaintiff did not state when she became aware defendant had de-med the claim a second time.

Under defendant’s policy, plaintiff had fifteen months after services were rendered to file smt. That time period expired February 2, 1994. Plaintiff filed smt July 29, 1994, almost twenty-one months after her hospitalization. Defendant then filed an exception of *790prescription, which the trial court referred to the merits.

After a bench trial, the court held plaintiffs condition was not preexisting and was covered by defendant’s policy. The court further held the case was not prescribed, stating: “It was not until after Dr. Hall’s November 1993 response that [plaintiff] could consider filing suit since she though[t] her claim was under review by [defendant]. Therefore, [plaintiff] was lulled into a sense of complacency; [defendant’s] argument of prescription is barred by the doctrine of contra non valentem. [Plaintiffs] suit was timely filed.”

Under the doctrine of contra non valentem agere nulla currit praescriptio, prescription does not run against a person unable to bring an action. A party excusably ignorant of a claim is not barred by prescription because one is not bound to do the impossible.1 The doctrine prevents the running of prescription where: 1) legal cause has prevented courts or their officers from acting on or taking cognizance of plaintiffs actions; 2) a condition coupled with a contract or connected with a proceeding has prevented the creditor from acting; 3) an act of the debtor has effectively prevented a creditor from availing himself of his cause of action; or 4) a cause of action is neither known nor knowable by plaintiff even though plaintiffs ignorance is not induced by defendant.2

The third type of contra non is most commonly invoked today. It is applicable when the defendant conceals information or misleads and lulls the plaintiff into inaction.3 It has been described as “an innocent plaintiff being lulled into a course of inaction in the enforcement of his right by reason of some concealment or fraudulent conduct on the part of the defendant, or because of [defendant’s] failure to perform Usóme legal duty whereby plaintiff has been kept in ignorance of his rights.”4 For example, in Matherne v. State Farm Mutual Automobile Insurance Company,5 State Farm advised plaintiff it would pay all of her damages. Two years later, after prescription had run, State Farm refused to pay her uninsured motorist claim. The court held that contra non suspended the running of prescription during the time State Farm led her to believe it would pay all her claims.

The supreme court explained in Lima v. Schmidt that “mere settlement offers or conditional payments, humanitarian or charitable gestures, and recognition of disputed claims” are not sufficient to suspend prescription.6 Furthermore, Louisiana Revised Statute 22:651 provides that investigating a claim does not waive any policy defenses:

None of the following acts by or on behalf of an insurer shall be deemed to constitute a waiver of any provision of a policy or of any defense of the insurer thereunder:

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(3) Investigating any loss or claim under any policy or engaging in negotiations looking toward a possible settlement of any such loss or claim.

Even if an insurer admits liability under a policy, unless it couples that admission with other acts and conduct that reasonably induce an insured to believe his claim will be settled without suit, the insurer is not *791precluded from invoking an applicable limitation in the policy.7 Unless the insurer in some manner leads the insured to reasonably believe the time limitation has been waived while the claim is under consideration or in some other way acts so as to induce the insured to withhold suit, the suit must be filed within the prescribed period, even if the claim is pending.8

The crucial determination is whether the overall actions of the insurer’s representatives during the prescriptive period led plaintiff to believe reasonably that Rthe insurer would not require compliance with the policy's prescriptive provision.9 The heart of this inquiry is the reasonableness of the plaintiff’s belief and inaction.10 An insured must show he exercised reasonable diligence in seeking the facts11 and asserting his rights. Prescription does not begin to run against a person who is ignorant of the facts upon which his cause of action is based, as long as such ignorance is not willful, negligent, or unreasonable.12

But the insured’s ignorance of his rights alone is not enough to trigger contra non. The insured must also prove the insurer committed some act, such as concealment, fraud, misrepresentation, or other ill practice, that tended to impede or prevent the insured from asserting his cause of action.13 Mere negligence or inadvertence on the part of the insurer is insufficient.14

The facts herein are very similar to those in Touro Infirmary v. Henderson,15 In that ease, Blue Cross denied a portion of Henderson’s claim within the prescriptive period. Henderson appealed the denial. Six months before the prescriptive period ended, Blue Cross advised Henderson it was reviewing her claim. Approximately a year later she filed suit. The court found her claim had prescribed and contra non was not applicable. It noted she knew from the time of her hospitalization that she had a potential claim against Blue Cross. She was aware of her claim and the policy provisions. Blue Cross never told her the claim would be paid, only that it was reviewing its prior denial; it never said her claim was likely to be approved. Furthermore, no representative of Blue Cross asked her not to file suit pending the investigation she requested. Under these facts, the court found Henderson was not prevented from protecting her claim by filing suit in a timely manner.

In this case, defendant did nothing to prevent or hinder plaintiff from filing suit. Plaintiff knew in January 1993 that defendant had denied her claim. She began a letter-writing campaign to defendant and the Louisiana Commissioner of Insurance to lehave that decision reversed. She testified she knew in July 1993 defendant was not going to pay, which is why she retained counsel. Defendant promised her nothing more than a review of its previous denial, all the while asserting it did not believe it had erred. Although defendant agreed in November 1993, three months before the prescriptive period ended, to review its denial once more, it in no way indicated it was waiving its right to claim the fifteen-month prescription provision in the policy.

*792The date on which prescription begins to run is a factual issue to be determined by the trier of fact. We review that determination under the clearly wrong standard.16 We find that in this case, the trial court was clearly wrong in finding prescription began to run in November 1993. Prescription began to run November 2, 1992. Plaintiffs action prescribed fifteen months later, on February 2, 1994. Thus, her suit filed July 29, 1994, was untimely. We must reverse the trial court and render judgment in defendant’s favor, dismissing plaintiffs suit.

For the foregoing reasons, the judgment of the trial court is reversed, and judgment is rendered in favor of Louisiana Health Service and Indemnity Company d/b/a Blue Cross and Blue Shield of Louisiana and against plaintiff, Loretta Webb, dismissing plaintiff’s suit. All costs are to be borne by plaintiff.

REVERSED AND RENDERED.