OPINION OF THE COURT
This matter comes on before this court on appeal from an order entered on December 3, 2002, affirming the final decision of the Commissioner of Social Security denying appellant Janice Newell’s (“New-ell”) request for widow’s disability benefits under Title II of the Social Security Act. The district court had jurisdiction pursuant to 42 U.S.C. § 405(g) and we have jurisdiction over Newell’s appeal pursuant to 28 U.S.C. § 1291. For the reasons set forth below, we will reverse the district court’s order affirming the Commissioner’s decision and instruct thе district court to remand the case to the Commissioner for further proceedings consistent with this opinion.
I. PROCEDURAL HISTORY AND FACTUAL BACKGROUND
A. Procedural History
Newell applied for widow’s disability benefits on November 16, 1998. To receive such benefits, Newell needed to demonstrate, inter alia, that she is (1) at least 50 but less than 60 years old; (2) the widow of a wage earner; and (3) under a disability as defined in 42 U.S.C. § 423(d)(2)(A). See 42 U.S.C. § 402(e)(1); 20 C.F.R. § 404.336. Newell, who was 56 years old at the time of her hearing before the ALJ, is the widow of wage earner Robert S. Newell. In her application for widow’s disability benefits, she alleged that she had been disabled since July 1, 1997, due to arthritis in her lower back and neck, a deteriorated disc, internal derangement of her knee, sciatica, and diabetes. At oral argument before this court, however, her attorney indicated that her disability is based solely on her liver disease, diabetes, and neuropathy. 1
The Social Security Administration (“SSA”) denied Newell’s application for widow’s disability benefits on April 20, 1999, and again upon reconsideration on June 17, 1999. Newell appealed аnd a hearing was held on February 9, 2000, before Administrative Law Judge (“ALJ”) Gerald J. Ryan. On April 17, 2000, ALJ Ryan issued a decision denying her application for benefits. His decision became final on April 16, 2001, after the Appeals Council denied Newell’s request for administrative review. On June 14, 2001, Newell filed a complaint in the district court challenging the Commissioner’s final ruling. The district court affirmed the final decision of the Commissioner on December 3, 2002. Newell thereafter filed this appeal.
B. Factual Background
Newell was born on August 1, 1943, and married Robert S. Newеll on August 31, 1968. Their marriage ended in divorce in June 1987, and she has not remarried. Her former husband, a wage earner, died fully insured for Social Security benefits on August 9, 1990, and Newell’s eligibility for widow’s benefits based on his earnings terminated at the close of the 84th month (seven years) after his death, on August 31, 1997, so that her disability had to have commenced by that date for her to be eligible for benefits. See 42 U.S.C. § 402(e)(1); 20 C.F.R. § 404.336(c)(1). 2
*543 From 1994 through December 1996, Newell was self-employed doing part-time consulting and craftwork. She estimates that she earned $5000 to $6000 per year during that time. From December 1996 through July 1997, she worked occasionally with a friend who was a carpenter, painting and making stained glass windows. She estimates that she earned $3000 per year during that time. In July 1997, New-ell injured her back when she tripped over a lawn mower. After that incident, she stopped working completely. She also stopped doing yardwork, gardening, washing, and cleaning.
Newell contends that she became disabled on July 1, 1997, but could not afford medical care at that time becausе she was uninsured. Beginning on June 1, 1998, however, she did seek medical attention when her father gave her the money to pay for it. Accordingly, most of the evidence in her record is comprised of doctors’ reports dated post August 31, 1997, the date upon which her eligibility for widow’s benefits expired. Newell contends that regardless of the dates on her medical reports, she is entitled to widow’s benefits because her medical conditions — liver disease, diabetes, and neuropathy — were present prior to August 31, 1997. She argues that these conditions are slowly progressive and that they disabled her within the period of her eligibility for benefits.
1. The Medical Evidence Before ALJ Ryan
The medical evidence consists of reports from Newell’s family doctor and her orthopedist, reports from the SSA in the form of a Residual Physical Functional Capacity Assessment and from a consultative examiner, as well as Newell’s testimony regarding her pain and functional limitations.
a. Medical Evidence Prior to August 31,1997
Billing records and an emergency room report indicate that Newell received services for treatment of an unstable low back and contusion of the wrist in 1990. Tr. 191-95, 199, 203. 3 Other billing statements and physical therapy reports from 1990 indicate that she was fitted for a custom molded lumbosacral corset, was instructed in home exercises and the use of a hot pack, and was treated for an unstable lower back. Tr. 195-98, 202. Prescriptions dated September 14, 1990, and November 21, 1990, indicate that she was prescribed over-the-counter nonsteroidal anti-inflammatories and Tylenol. Tr. 194, 196, 200. In December 1990, she was referred for electromyogram (“EMG”) and nerve conduction studies. Tr. 200-01. Another billing statement reflects that she received emergency room services on December 10, 1993, for shoulder joint pain. Tr. 204.
b. Post-Coverage Medical Evidence (After August 31,1997)
Most of the medical evidence is comprised of doctors’ reports dated post August 31, 1997. Newell first went to Dr. Harold Chaflan, her family physician, on June 1, 1998. Dr. Chaflán treated her diabetes and the pain in her knees and back. On August 12, 1998, she began treatment with an orthopedist, Dr. Alfred Greisman. In his notes, Dr. Greisman mentiоned Newell’s liver condition, stating that he was “apprehensive about putting her on any nonsteroidals because of her liver condition.” Tr. 152. His records indicate that Newell lost 50 pounds in 1998. Tr. 149. The 50 pounds apparently included 40 pounds of muscle. Tr. 155. *544 On September 17, 1998, Dr. Greisman concluded that “due to her condition she is unable to drive or travel.” Tr. 151. In November 1998, Newell underwent an EMG, which indicated results consistent with peripheral neuropathy. Tr. 145.
The medical evidence from the SSA includes a Residual Physical Functional Capacity Assessment by a non-treating physician dated December 15, 1998, and a report from consultative examiner Dr. Phillip B. Eatough dated March 11, 1999. Tr. 156-63; 164-67. The Residual Physical Functional Capacity Assessment indicates that Newell occasionally could lift and/or carry 20 pounds; frequently lift and/or carry ten pounds; stand and/or walk for about six hours in an eight-hour workday; sit for a total of about six hours in an eight-hour workday; and push and pull without limitation.
Consultative examiner Dr. Eatough noted in his report that Newell hаd endured gradual and progressive back problems for approximately seven years; neuropathy for approximately two years, possibly related to her diabetes or alcohol excess; and diabetes for about two years. He also noted that when she stopped drinking alcohol, she lost about 45 pounds. Tr. 164^66.
Dr. Eatough’s impressions included (1) peripheral neuropathy with bilateral carpal tunnel syndrome and neuropathy of both lower extremities with possible atrophy of the proximal muscle groups; (2) diabetes mellitus most probably secondary to chronic alcohol consumption; (3) peripheral vascular disease; (4) osteoarthritis with low back syndrome, possible sciatica and lumbar neuropathy; and (5) liver dysfunction. He found that she occasionally could lift 20 pounds; frequently lift ten pounds; stand and walk approximately two hours in an eight-hour workday without a required assistive device; and sit about six hours in an eight-hour workday with periodic standing. He found that her аbility to push and pull was limited in the upper and lower extremities secondary to tenderness and neuropathy. He reported that she occasionally could climb, balance, stoop, kneel, crouch, and crawl. He found no manipulative, visual, communicative, or environmental limitations. Tr. 166-67.
Less than two months later, on May 1, 1999, Newell’s family physician, Dr. Chai-kin, reported that Newell “is crippled by severe peripheral neuropathy secondary to diabetes and alcohol consumption.” He noted that her prognosis “is poor.... She has been seen by the neurologists, by the orthopedists and myself and, unfortunately, we have come up with no answer for this poor woman’s pain which will negate her being gainfully employed in any manner whatsoever.” Tr. 142.
2. Newell’s Testimony Before the ALJ
Newell testified that at the time of her hearing, she was taking prescription pain relievers, sleep aids, and oral medication for diabetes. She was also taking nonprescription pain relievers and vitamins. She wore splints fоr her wrists and a brace for her back. She testified that her pain was severe and that it had prevented her from working or doing any housework since July 1997, when she fell over a lawnmower and hurt her back. Tr. 31, 43. She did not seek medical attention until June 1998 because she had no insurance. Tr. 32. When she went to the doctor, he diagnosed her with diabetes and neuropa-thy. Tr. 33-34. She testified that she is unable to bathe, dress herself, and drive. Tr. 43-44.
3. The ALJ’s Findings
ALJ Ryan found that Newell’s allegations were not supported by objective medical еvidence and were contradicted by her own statements and actions. He not *545 ed, for example, that there was no evidence that Newell sought or received regular medical treatment from 1990 to 1998. Nor did she receive treatment for her back injury in 1997. ALJ Ryan also found that it was not until August 1998, a year after she was last eligible for benefits, that she began to experience neuropathy in her lower extremities and that her medical problems worsened. Thus, he concluded that prior to August 31, 1997, she did nоt have a severe impairment that lasted or could be expected to last 12 months or more, which significantly limited her ability to engage in work-related activities. Accordingly, he determined that she was not entitled to widow’s disability benefits.
II. DISCUSSION
A. Standard of Review
We exercise plenary review over the order of the district court,
see Knepp v. Apfel,
B. Statutory and Regulatory Framework
In order to establish a disability under the Social Security Act, a claimant must demonstrate that there is some “ ‘medically determinable basis for an impairment that prevents him from engaging in any “substantial gainful activity” for a statutory twelve-month period.’ ”
Stunkard v. Secretary of Health & Human Servs.,
The SSA has promulgated regulations incorporating a five-step sequential evaluation process for determining whether a claimant is under a disability.
See
20 C.F.R. § 404.1520;
Williams v. Sullivan,
If the claimant is unable to resume his former occupation, the evaluation moves to the final step. Id. At this stage, the burden of production shifts to the Commissioner, who must demonstrate the claimant is capable of performing other available work in order to deny a claim of disability. Id. The Commissioner must show there are other jobs existing in significant numbers in the national economy which the claimant can perform, consistent with his or her medical impairments, age, education, past work experience, and residual functional capacity. Id. The ALJ must analyze the cumulative effect of all the claimant’s impairments in determining whether he is capable of performing work and is not disabled. Id. at 118-19.
C. The Step-Two Determination
As mentioned above, at step two of the five-step sequential inquiry the ALJ determines whether the claimant has a medically severe impairment or combination of impairments.
See Bowen v. Yuckert,
The step-two inquiry is a
de minimis
screening device to dispose of groundless claims.
See Smolen v. Chater,
1. The ALJ Denied Newell’s Claim At Step Two on Erroneous Bases
According to ALJ Ryan, the objective medical evidence in Newell’s record did not support her allegation of disability and thus he denied her claim at step two of the sequential evaluation. It is true that her record lacks evidence of treatment for liver disease, diabetes, or neuropathy prior to August 31, 1997. Nonetheless, this lack of evidence in the particular circumstances of this case did not provide an adequate basis to support a conclusion that Newell was not disabled prior to August 31, 1997. We note that several courts have questioned the relevance of infrequent medical visits in determining when or whether a claimant is disabled. For example, the Court of Appeals for the Ninth Circuit has held that the fact that a “claimant may be one of the millions of people who did not seek treatment for a mental disorder until late in the day” was not a substantial basis to reject that an impairment existed.
Nguyen v. Chater,
In fact, SSR 96-7p, 1996 SSR LEXIS 4, at *22, states that “the adjudicator must not draw any inferences about an individual’s symptoms and their functional effects from a failure to seek or pursue regular medical treatment without first considering any explanations that the individual may provide, or other information in the case record, that may explain infrequent or irregular medical visits or failure to seek medical treatment.” Here, Newell’s explanation for her failure to seek treatment prior to August 31, 1997, is adequate — she claims she could not afford treatment until her father gave her money in June 1998. Moreover, the record demonstrates that her income during the germane period was very low and that she did not have medical insurance, circumstances that support her claim that she could not afford treatment. Accordingly, we disagree with the ALJ’s statement that “[i]t is reasonable to assume that if [Newell] was experiencing the degree of pain and functional limitation which she has alleged that she would have sought medical treatment.” Tr. 16.
It is Newell’s position that her liver disease, diabetes, and neuropathy are slowly progressing conditions that existed well before their documentation in 1998. She argues that her medical record must be studied retrospectively to determine when her medical conditions actually becamе disabling. Retrospective diagnosis of an impairment, even if uncorroborated by contemporaneous medical records, but corroborated by lay evidence relating back to the claimed period of disability, can support a finding of past impairment.
See Loza v. Apfel,
The ALJ also erred in using Newell’s lack of treatment prior to August 31, 1997,
*548
as a basis for discrediting her credibility regarding her pain and level of function. Lay evidence need not be corroborated by contemporaneous medical evidence to be credible.
See Basinger v. Heckler,
2. The ALJ Failed To Apply SSR 83-20
SSR 83-20, 1983 SSR LEXIS 25, provides ALJs with an analytical framework for determining a disability onset date. SSR 83-20 defines the “onset date of disability” as “the first day an individual is disabled as defined in the Act and the regulations.” Id. at *1. In cases in which the onset date is critical to a determination of entitlement to benefits, an ALJ must grapple with and adjudicate the question of onset, however difficult. See id. (“In addition to determining that an individual is disabled, the decisionmaker must also establish the onset date of disability. In many claims, the onset date is critical; it may ... even be determinative of whether the individual is entitled to or eligible for any benefits.”). 6
Here, the ALJ’s task was to determine when, if ever, Newell’s liver disease, diabetes, and neuropathy became disabling. According to SSR 83-20, id. at *6-7,
[wjith slowly progressive impairments, it is sometimes impossible to obtain medical evidence establishing the precise date an impairment became disabling. Determining the proper onset date is particularly difficult, when, for example, the alleged onset and the date last worked are far in the past and adequate medical records are not available. In such cases, it will be necessary to infer the onset date from the medical and other evidence that describe the history and symptomatology of the disease process.
In some cases, it may be possible, based on the medical evidence to reasonably infer that the onset of a disabling impairment(s) occurred some time prior to the date of the first recorded medical examination.... How long the disease may be determined to have existed at a disabling level of severity depends on an informed judgment of the facts in the particular case. This judgment, however, must have a legitimate medical basis. At the hearing, the administrative law judge (ALJ) should call on the services of a medical advisor when onset must be inferred.
If reasonable inferences about the progression of the impairment cannot be *549 made on the basis of the evidence in file and additional relevant medical evidence is not available, it may be necessary to explore other sources of documentation. Information may be obtained from family members, friends, and former employers to ascertain why medical evidencе is not available for the pertinent period and to furnish additional evidence regarding the course of the individual’s condition.
Newell is correct that the ALJ in this case failed to follow this formula. The ALJ should have consulted a medical ad-visor to help him infer the onset date as required by SSR 83-20 and our decision in
Walton v. Halter,
III. CONCLUSION
A district court, after reviewing the. decision of the Commissioner may under 42 U.S.C. § 405(g) affirm, modify, or reverse the Commissioner’s decision with or without a remand to the Commissioner for a rehearing.
See Podedworny v. Harris,
For the foregoing reasons we will reverse the order of December 3, 2002, and will remand the case to the district court to remand it in turn to the Commissioner *550 for further proceedings in accordance with this opinion.
Notes
. The Commissioner has not contended that we should not consider this case on the basis of Newell allegedly being disabled for the reasons she emphasized at oral argument.
. Originally, Newell argued that her eligibility for widow’s benefits ran until August 1998, but at oral argument her attorney abandoned that argument and thus accepted August 31, 1997, as the cut-off date.
. Tr. refers to the administrative transcript.
. Social Security Rulings constitute the SSA's interpretations of the statute it administers and of its own regulations.
Chavez v. Dep’t of Health & Human Servs.,
. SSR 85-28, 1985 SSR LEXIS 19, at *11-12, states that “[g]reat care should be exercised in applying the not severe impairment concept. If an adjudicator is unable to determine clearly the effect of an impairment or combination of impairments on the individual’s ability to do bаsic work activities, the sequential evaluation process should not end with the not severe evaluation step. Rather, it should be continued.”
. Under SSR 83-20, 1983 SSR LEXIS 25, at *3, an ALJ should consider three factors in determining an onset date: (1) the claimant’s allegations; (2) the claimant’s work history; and (3) medical and other evidence.
. In Walton, we held that the ALJ must call upon the services of a medical advisor in a situation where the alleged impairment was a slowly progressing one, the alleged onset date was far in the past, and adequate medical records for the most relevant period were not available. See id. at 709.