LAY, Senior Circuit Judge.
Garnet L. Morse appeals from the district court’s2 order affirming the Secretary of [868]*868Health and Human Services’ (“the Secretary”) denial of Ms. Morse’s application for supplemental security income (“SSI”) benefits under Title XVI of the Social Security Act, 42 U.S.C. §§ 1381-1383c (1988 & Supp. III 1991). This is her fourth application: She filed her previous applications in 1984, 1988, and 1989. Each application was denied throughout the administrative process. Although the claimant asserts disability since 1975, the denial of her latest application on September 25,1989, remains binding and her present claim filed on March 14, 1990, required the Secretary to determine her disability on the basis of evidence obtained since September 25, 1989. Her past history, prior to September 25, 1989, is referred to for foundational purposes only. The Administrative Law Judge (“AL J”) granted the claimant a hearing on February 27, 1991, and subsequently denied her claim. The appeals council denied a request for review. Upon petition for review, the district court found that there existed substantial evidence on the record as a whole to support the Secretary’s denial of the claim. We reverse and remand.
I.
Ms. Morse was forty-eight years old at the time she filed her fourth application for SSI benefits. She has completed the eleventh grade, has a very limited work history, and her only past relevant work is that of a sandwich maker. Since 1975 she has had recurrent cardiac, pulmonary and low back problems and has undergone surgery for her cardiac condition. She has had at least two hospitalizations for both her pulmonary and low back problems since the time when her third application was denied in September of 1989.
In March of 1989, her treating physician, a certified board internist, Dr. Wilson L. Davis, summarized her past and present diagnosis as follows:
Mrs. Morse’s current diagnoses include: rheumatic heart disease with severe mitral stenosis, status post mitral commissuroto-my; left lower extremity radiculopathy probably secondary to protruding disc; congestive heart failure compensated on limited activity and medication; chronic atrial fibrillation; history of angina pector-is; history of depression; history of frequent pneumonias and episodes of asthmatic bronchitis.
This diagnosis was confirmed in a letter to Dr. Davis from a consulting physician, Dr. Charles McKay, at the University of Iowa Hospitals and Climes (“UIH”). After examining Ms. Morse in December of 1989, Dr. McKay’s diagnosis of Ms. Morse was:
Your patient was seen in the Cardiology Clinic on December 27, 1989 with the following diagnoses: 1) rheumatic mitral stenosis, status post valvuloplasty on August 18,1989 and commissurotomy in 1976; 2) chrome atrial fibrillation with periodic pulmonary edema; 3) status post cholecys-tectomy; 4) L4 and L5 disc narrowing with low back and left leg pain; 5) chronic urinary tract infections of Klebsiella.
On September 18,1990, Dr. Davis presented a final diagnosis of the claimant after a week-long period of hospitalization in which he observed:
FINAL DIAGNOSIS:
1. Severe back and left leg pain due to bulging L5-S1 discs exacerbated by a recent fall with associated muscle spasm.
2. Rheumatic heart disease with mitral stenosis, status post mitral valve com-missurotomy in 1976 and balloon valvulo-plasty in May 1990.
3. Congestive heart failure.
4. Atrial fibrillation.
5. Moderate appearing mitral regurgitation and mild aortic and pulmonic regurgitation.
6. History of depression.
7. Status post cholecystectomy.
At that time, Dr. Davis opined that as of May 29, 1990, Ms. Morse was still suffering from congestive heart failure. He added:
I believe that Mrs. Morse is disabled as far as regular work is concerned. She would be restricted from lifting more than perhaps 20 pounds and would be unable to carry even smaller amounts more than a few feet at a time. She does not appear to be restricted as far as standing, moving about and sitting but would be limited as [869]*869far as walking because of her mitral valvular disease and her congestive heart failure. She would have considerably limited stooping, climbing, kneeling and crawling and could not be expected to do this in a job situation because of her lumbar disc disease which continues to cause continuous pain even when she is resting.
I do not believe Mrs. Morse has difficulty with handling objects, seeing, hearing, speaking or traveling. She could not be exposed to environments involving fumes, high or low temperatures or hazards such as climbing or being in high places because of her heart disease.
On December 29, 1990, Dr. Davis observed:
Mrs. Morse was admitted to the hospital on 10/30/90 and discharged on 11/5/90. I am enclosing a copy of the discharge summary. I believe that this hospitalization again reflects the fact that Mrs. Morse has several medical problems and although she is able to function moderately well under the best of circumstances even a small perturbation, from normal may lead to significant decompensation in her overall condition.
I subsequently saw Mrs. Morse on 11/13/90. She showed good improvement in her back pain although she continued to have muscle tenderness. It was noted that she continues to be followed at University of Iowa Hospitals for her heart condition which I consider to be only marginally compensated. It continues to be my belief based on this and previous exposure to this patient that she is disabled from both a cardiac and a lumbar disc perspective, (emphasis added)
We deem it appropriate in view of the denial of the claim that her progress notes prepared by Dr. Davis be set forth in the margin. Although these notes begin in 1986, we include material portions of this history subsequent to September 1989.3
[870]*870ii.
In reviewing the ALJ’s decision to deny disability benefits, we must ascertain “whether there is substantial evidence on the record as a whole to support” the Secretary’s decision. Hutsell v. Sullivan, 892 F.2d 747, 748-49 (8th Cir.1989). This review involves more than a search of the record for evidence supporting the Secretary’s findings; the substantial evidence test requires that we take into account evidence that fairly detracts from the Secretary’s decision. Thomas v. Sullivan, 876 F.2d 666, 669 (8th Cir.1989).
An individual is considered to be impaired if she is “unable to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to ... last for a continuous period of not less than twelve months.” 42 U.S.C. § 1382c(a)(3)(A). The physical or mental impairment must be of such severity that the applicant is “not only unable to do his previous work but cannot, considering his age, education, and work experience, engage in any other kind of substantial gainful work which exists in the na[871]*871tional economy.” Id. § 1382c(a)(3)(B). If the applicant asserts that she has multiple impairments, the Act requires the Secretary to “consider the combined effect of all of the individual’s impairments without regard to whether any such impairment, if considered separately, would be of such severity.” Id. § 1382c(a)(3)(F).
A five step sequential analysis is followed in determining whether a claimant is disabled. See 20 C.F.R. § 416.920 (1993). The first step asks if the claimant is currently engaged in substantial gainful employment. If so, the claimant is not disabled. If not, the second step inquires if the claimant has an impairment or combination of impairments that significantly limits the ability to do basic work activities. If not, the claimant is not disabled. If so, the third step is whether the impairments meet or equal a listed impairment; if they do, the claimant is disabled. The fourth step asks if the claimant’s impairments prevent her from doing past relevant work. If the claimant can perform past relevant work, she is not disabled. The fifth step involves the question of whether the claimant’s impairments prevent her from doing other work. If so, the claimant is disabled. Once the applicant demonstrates, under the fourth step, impairments that prevent her from returning to her previous work, the burden shifts to the Secretary to prove that jobs exist in the national economy that the applicant could perform. Cline v. Sullivan, 939 F.2d 560, 564 (8th Cir.1991).
The Secretary found that the claimant’s disability did prevent her from performing her past relevant work as a sandwich maker. Based upon the ALJ’s assessment of her disability and the vocational expert’s response to hypothetical questions, however, the ALJ held that notwithstanding the claimant’s severe impairment she had sufficient residual functional capacity to perform other substantial gainful work within the national economy. Thus, the claimant was denied benefits because of the ALJ’s findings on the fifth step of the sequential analysis under 20 CFR § 416.920.
In assessing the claimant’s disability, the ALJ rejected her subjective complaints of disability, shortness of breath, chest pain, lower back pain and occasional leg pain. The ALJ, although agreeing that the claimant suffered from a “severe” impairment, nevertheless rejected the treating physician’s opinion that the claimant was “disabled” under the Act. The ALJ reasoned:
Although [Dr. Davis] opined the claimant was “disabled” at Exhibit B-86, he went on to note the claimant could lift up to 20 pounds, could carry less than 20 pounds, and had unlimited abilities to stand, sit, and move about. Clearly, his thoughts as to what makes a person “disabled” do not coincide with the statutes and regulations governing the Social Security Administration. Furthermore, the claimant’s treating physicians at the University of Iowa Hospitals and Clinics have not opined the claimant is disabled because of her cardiac and back problems. Indeed, at Exhibit B-77, the claimant was reported as being only somewhat limited by her cardiac disease and lower back pain, and at Exhibit B-93 was reported as having only mild pulmonary disease which was not limiting and significant cardiac disease which was only mildly limiting. Accordingly, the undersigned discounts the opinion of Dr. Davis that the claimant is “disabled.”
The ALJ further found that the claimant’s daily activities were inconsistent with disability. Based upon a hypothetical question, the vocational expert opined that there were approximately 500 positions available in Iowa and 25,000 positions available nationwide that the claimant could perform.
We find that there does not exist substantial evidence on the record as a whole to substantiate that the claimant possessed sufficient residual functional capacity to perform substantial gainful activity under the fifth sequential step. In reviewing the record as a whole, we find that the Secretary presented no medical evidence that contradicts Dr. Davis’s opinion regarding the claimant’s disability. Dr. Davis has treated the claimant since 1986. He utilized the reports from the specialists at the University of Iowa Hospitals and Clinics in making his evaluation. In formulating the hypotheticals and reaching the conclusion that Ms. Morse is not [872]*872disabled, the ALJ discredited Dr. Davis’s findings, and mistakenly believed that Ms. Morse’s ability to do light housework was inconsistent with disability. The ALJ also held the claimant’s limited work history against her. In addition, the Secretary improperly rejected the claimant’s subjective pain, notwithstanding the hospital’s medical records which overwhelmingly support these findings.
A Ms. Morse’s Subjective Complaints of Pain
In assessing the claimant’s disability and formulating the hypothetical questions posed to the vocational expert, the ALJ rejected Ms. Morse’s subjective complaints of pain. Specifically, the ALJ found: “The allegations of the claimant regarding her subjective complaints of disabling shortness of breath, chest pain, lower back pain, and occasional leg pain are not found to be credible for the reasons discussed in the body of this decision.” The ALJ’s decision does not, however, reveal the reasons for discounting Ms. Morse’s complaints. Regarding Ms. Morse’s complaints of lower back pain and left leg pain, the ALJ simply states that “there is no evidence of significant limitation of motion” and “the claimant has experienced only a moderate restriction of activities of daily living.” As far as shortness of breath and chest discomfort, the ALJ notes that at one point the claimant stated that she experienced only some shortness of breath and chest discomfort.
As we have explained on numerous occasions, for an ALJ to reject a claimant’s subjective complaints of pain, the ALJ must “make an express credibility determination explaining his reasons for discrediting the complaints.” Ghant v. Bowen, 930 F.2d 633, 637 (8th Cir.1991); see also Delrosa v. Sullivan, 922 F.2d 480, 485 (8th Cir.1991); Prince v. Bowen, 894 F.2d 283, 286 (8th Cir.1990). Furthermore, because evidence of such pain is frequently subjective and difficult to evaluate, we do not require direct medical evidence linking the physical problems and the subjective complaints of pain. See Tucker v. Schweiker, 689 F.2d 777, 780-81 (8th Cir.1982) (per curiam). Rather, the ALJ is to expressly determine if the claimant’s complaints are credible.
In the present case, the ALJ failed to explain why he chose to reject Ms. Morse's complaints. Although the ALJ is in the best position to make credibility determinations, he is not given unfettered discretion to dismiss subjective complaints of pain without providing some basis for this decision. The record reveals that Ms. Morse’s complaints are supported by medical evidence and the ALJ’s decision contains no indication of why her complaints were discredited. Hence, we find that the ALJ improperly discredited Ms. Morse’s complaints of pain and should have included all of them in the hypothetical questions posed to the vocational expert.
B. Dr. Davis’s Credibility
The ALJ rejects Dr. Davis’s findings regarding the degree of Ms. Morse’s impairments based in part on the ALJ’s finding that Dr. Davis is not qualified to say whether the claimant is disabled under the Social Security Act (the “Act”). The ALJ asserts that Dr. Davis is not familiar with the Act and regulations and that it is exclusively the ALJ’s prerogative to find that she is or is not disabled. While it is true that the ALJ applies the Act and regulations to determine if a claimant is considered disabled under the Act, the ALJ may not simply disregard a credible medical opinion in making this determination.
Initially, the ALJ’s observations are not grounds for rejecting the findings of a board certified internist. The treating physician has the best opportunity to observe and evaluate a claimant’s condition. This court has on repeated occasions emphasized that the treating physician’s evidence must be given great weight, with deference to the physician’s findings over an examining physician or consultant. See Thompson v. Sullivan, 957 F.2d 611, 614 (8th Cir.1992); Henderson v. Sullivan, 930 F.2d 19, 21 (8th Cir.1991); Hancock v. Secretary of the Dep’t of Health, Educ. and Welfare, 603 F.2d 739, 740 (8th Cir.1979) (“[T]he report of a consulting physician who examined the claimant once does not constitute ‘substantial evi[873]*873dence’ upon the record as a whole, especially when contradicted by the evaluation of the claimant’s treating physician.” (citations omitted)); Veal v. Califano, 610 F.2d 495, 497-98 (8th Cir.1979) (written report of non-examining physicians entitled to little weight in overall evaluation of disability); Landess v. Weinberger, 490 F.2d 1187, 1189-90 (8th Cir.1974).
The fact that a physician is not trained in the statutes and regulations of the Social Security Act does not preclude the physician from evaluating the claimant. The physician’s findings and conclusions constitute substantial evidence which must be carefully weighed by the ALJ and the Secretary. Unless there is medical evidence that contradicts or refutes the physician’s medical conclusion, the Secretary is bound to treat the treating physician’s diagnosis and conclusion as substantial evidence.4 Bastien v. Califano, 572 F.2d 908, 912 (2d Cir.1978); see also Whitney v. Schweiker, 695 F.2d 784, 789 (7th Cir.1982) (“If the ALJ concludes that a treating physician’s evidence is credible, therefore, he should give it controlling weight in the absence of evidence to the contrary because of the treating physician’s greater familiarity with the plaintiffs conditions and circumstances.” (citations omitted)).
There is no medical evidence to contradict Dr. Davis’s findings and no evidence indicating that Dr. Davis is not credible. The ALJ apparently thought that two statements made by Dr. McKay were inconsistent with Dr. Davis’s diagnosis. On March 29, 1990, Dr. McKay wrote that Ms. Morse is “somewhat limited” by her cardiac disease and low back pain and is “somewhat disabled.” On December 14, 1990, Dr. McKay opined that Ms. Morse has significant cardiac disease which was stable and mildly limiting at that time, that her pulmonary disease was not limiting, and that Ms. Morse’s back and leg pain seem to be the most limiting of her problems. It is important to note that Dr. McKay is a member of the Cardiovascular Diseases Division at UIH, and that his area of specialization does not encompass pulmonary disease or problems associated with the back or legs.
It was for Dr. Davis, Ms. Morse’s treating physician, to consider Dr. McKay’s cardiac evaluations in conjunction with Ms. Morse’s other impairments. Thus, even if Dr. McKay states that Ms. Morse is “mildly disabled,” this does not contradict Dr. Davis’s finding of more severe impairment which is based upon his consideration of the combined effect of all of the claimant’s impairments. See 42 U.S.C. § 1382c(a)(3)(F); Delrosa v. Sullivan, 922 F.2d 480, 484 (8th Cir.1991) (ALJ is required to consider the combined effects of claimant’s impairments); see generally Donato v. Secretary of the Dep’t of Health and Human Servs., 721 F.2d 414, 419-20 (2d Cir.1983) (although findings of non-treating physicians were somewhat inconsistent with treating physician’s, they were “not so completely at odds with his diagnosis” particularly where all parties agreed that claimant suffered from serious impairments).
In contrast to Dr. Davis, the ALJ is not a medical expert and cannot by his legal expertise discount and reject the medical findings and conclusions of the physician. His role is not to make a personal estimate of the claimant’s impairments but to base his findings on whether the credible evidence before him sustains or does not sustain the claimant’s asserted disability. In this case, the ALJ has made medical and psychological conclusions without substantial evidence to support his findings.
C. Ms. Morse’s Daily Living Routine
The ALJ also discounts Dr. Davis’s conclusion of disability because he finds Ms. Morse’s daily living routine to be inconsistent with disability. The ALJ recites that the claimant gets up in the morning and is awake during regular hours, she does the dishes and laundry and is able to read, when her [874]*874daughter visits she helps her daughter watch her two small grandchildren, she has dinner at home or her daughter’s, she attends church, she does light cleaning once a week, she cooks three to four times a week and shops once a month.
These minimal activities do not refute the fact that the claimant cannot perform substantial gainful activity. Disability under the Social Security Act does not mean total disability or exclusion from all forms of human and social activity. See Harris v. Secretary of the Dep’t of Health and Human Servs., 959 F.2d 723, 726 (8th Cir.1992) (claimant’s ability to cook, shop, clean, do laundry and visit friend does not constitute substantial evidence that claimant can engage in substantial gainful activity); Thomas, 876 F.2d at 669 (“[A] claimant need not prove she is bedridden or completely helpless to be found disabled.”); Jeffcoat v. Bowen, 840 F.2d 592, 596 (8th Cir.1988).
D. Ms. Morse’s Work History
The ALJ cites the claimant’s limited work history, reasoning that such a limited history does not operate in favor of the claimant’s attempt to establish disability impairment. The claimant’s medical history demonstrates that she has not been the best candidate for continued employment. The fact that she has not worked most of her adult life does not prove or disprove her present status of disability under the Act. It certainly does not serve as evidence to refute Dr. Davis’s diagnosis.
E. Jobs in the National Economy
Not only does Dr. Davis’s diagnosis stand uncontradicted, but the Secretary has not shown that a significant number of jobs exist in the national economy which Ms. Morse is able to perform. The ALJ relies on the opinion of a vocational expert who testified that Ms. Morse could perform sedentary unskilled positions and that there were 5,000 positions of sedentary work in Iowa (250,000 positions in the United States) which the claimant could perform. When informed that the claimant could not stoop, bend repetitively, climb, kneel or crawl, must alternate sitting with standing with no more than forty-five minutes in one position, and could do only simple repetitive tasks, the vocational expert altered his opinion and said there were only 500 positions in Iowa (25,000 in the United States).
In order to rely on a vocational expert’s opinion, “the hypothetical question posed to a vocational expert must fully set forth a claimant’s impairments.” Totz v. Sullivan, 961 F.2d 727, 730 (8th Cir.1992) (citing Shelltrack v. Sullivan, 938 F.2d 894, 898 (8th Cir.1991)). If a hypothetical question does not include all of a claimant’s impairments, limitations and restrictions, or is otherwise inadequate, a vocational expert’s response cannot constitute substantial evidence to support a conclusion of no disability. See id.; Greene v. Sullivan, 923 F.2d 99, 101 (8th Cir.1991).
The hypothetical posed to the vocational expert in this case is inadequate for a number of reasons and as a result the vocational expert’s opinion cannot serve as a basis for denying benefits to Ms. Morse. One of the most disturbing aspects of the hypothetical is the use of a stress test. In posing the hypothetical, the ALJ asked the vocational expert to assume that the claimant could handle a stress level of six on a scale of one to ten. There is no psychological test in evidence to support such an assumption. The ALJ admittedly created this test from his own determination of what stress levels certain jobs might involve and picked the score of six as the amount of stress that the claimant could endure. There is no medical evidence to support the ALJ’s assumptions, and a hypothetical question based solely upon the ALJ’s assumptions, without medical corroboration, is devoid of usefulness or meaning. See Mitchell v. Sullivan, 925 F.2d 247, 249-50 (8th Cir.1991) (rejecting the ALJ’s assignation of a stress level of five on a one to ten scale because there was no medical corroboration that claimant could withstand a moderate level of stress); Douglas v. Bowen, 836 F.2d 392, 396 (8th Cir.1987). More importantly, Dr. Davis’s opinion reflects that the claimant is unable to handle the stress which results from exertion: she becomes very depressed, cannot sleep and [875]*875cries. See Delrosa, 922 F.2d at 484 (improper for ALJ to substitute his “own unsubstantiated conclusions” regarding claimant’s medical condition for that of the treating physician).
The hypothetical was also deficient because it failed to disclose that this claimant has for the past several years, and particularly since September of 1989, been under constant medical care for her back, her heart, her depression and her pulmonary problems. No employer would consider her employable. See Douglas v. Bowen, 836 F.2d 392, 396 (8th Cir.1987) (vocational expert acknowledged that claimant could not find work in the national economy if he had more than two absences a month due to his impairments); Dobrowolsky v. Califano, 606 F.2d 403, 408 & n. 16 (3d Cir.1979) (noting that most jobs require regular attendance).
The hypothetical question completely ignored the claimant’s unrefuted testimony that her daily activities were extremely limited. She testified she could not sit for more than two or three minutes at a time depending on the type of chair. She could stand for only five to ten minutes. She slept only two to four hours a night, sometimes waking every hour. She was under constant medication. She took Lasix, Lanoxin, Coumadin, Potassium, used an inhaler and carried nitroglycerin at all times. She had to lay down throughout the day. It is unrealistic to think that a person with such medical conditions and limitations of motion and exertion could perform substantial gainful activity even on a part-time basis. See Mitchell v. Sullivan, 925 F.2d 247 (8th Cir.1991) (claimant found disabled where he could not perform jobs requiring physical or mental stress and jobs identified by vocational expert had near moderate degree of stress associated with them); Ferguson v. Schweiker, 765 F.2d 31, 36 (3d Cir.1985); Delgado v. Heckler, 722 F.2d 570, 574 (9th Cir.1983) (“A man who cannot walk, stand or sit for over one hour without pain does not have the capacity to do most jobs available in the national economy.”).
Finally, in determining that a significant number of jobs exist which Ms. Morse could perform, the vocational expert found that Ms. Morse had no transferable skills and opined that she could perform work only at an unskilled level, including the “unskilled clerk positions of reviewer, sorter and checker.” The Secretary now concedes on this appeal that the Dictionary of Occupational Titles (4th ed. 1991) lists these jobs at a skill level higher than that of unskilled. The Secretary urges that the issue of skill level was not raised at the district court level. The court is free, however, to take judicial notice of the Secretary’s own rules and regulations. See Roemer v. Board of Public Works of Maryland, 426 U.S. 736, 742 n. 4, 96 S.Ct. 2337, 2343 n. 4, 49 L.Ed.2d 179 (1976); Ray v. Aztec Well Svc. Co., 748 F.2d 888, 889 (10th Cir.1984); International Brotherhood of Teamsters, Chauffeurs, Warehousemen and Helpers of America v. Zantop Air Transport Corp., 394 F.2d 36, 40 (6th Cir.1968). Without deciding whether 500 jobs in the state of Iowa is sufficient, we simply point up the shortcoming of the vocational expert in stating that these jobs are available for unskilled labor and including them in the jobs which Ms. Morse allegedly could perform.
We find the ALJ’s hypothetical question not only misleading as to the claimant’s ability to handle stress and her need for constant medical care, but the vocational expert’s response relating to unskilled jobs must be discounted in weighing the overall record for substantial evidence. Because the hypothetical question did not adequately present the full extent of Ms. Morse’s impairments and in light of the vocational expert’s failure to properly identify jobs which Ms. Morse may be capable of performing, the vocational expert’s opinion cannot constitute substantial evidence to support a conclusion of no disability.
III.
We find that substantial evidence on the record as a whole does not support the Secretary’s determination that the claimant retained sufficient residual functional capacity to perform substantial gainful activity. The medical opinion and the overall record clearly support a finding of disability under the Act and, in light of the flawed hypothetical, the Secretary has not shown that jobs exist in [876]*876the national economy which the claimant could perform.
The judgment of the district court is reversed. The case is remanded to the Secretary with directions to grant supplemental social security income to the claimant.